H555-01 Linear, Angular, Projectile Motion by Ullswater Community College

Physical Education (A level) Linear, Angular, Projectile Motion C Jones Please note that you may see slight differences between this paper and the original.

Duration: Not set

Candidates answer on the Question paper. OCR supplied materials: Additional resources may be supplied with this paper. Other materials required: • Pencil • Ruler (cm/mm)

INSTRUCTIONS TO CANDIDATES • • • • • •

Write your name, centre number and candidate number in the boxes above. Please write clearly and in capital letters. Use black ink. HB pencil may be used for graphs and diagrams only. Answer all the questions, unless your teacher tells you otherwise. Read each question carefully. Make sure you know what you have to do before starting your answer. Where space is provided below the question, please write your answer there. You may use additional paper, or a specific Answer sheet if one is provided, but you must clearly show your candidate number, centre number and question number(s).

INFORMATION FOR CANDIDATES • The quality of written communication is assessed in questions marked with either a pencil or an asterisk. In History and Geography a Quality of extended response question is marked with an asterisk, while a pencil is used for questions in which Spelling, punctuation and grammar and the use of specialist terminology is assessed. • The number of marks is given in brackets [ ] at the end of each question or part question. • The total number of marks for this paper is 133. • The total number of marks may take into account some 'either/or' question choices.

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Answer all the questions.

1(a).

A gymnast successfully completes a double somersault. Define the terms ‘angular distance’ and ‘angular displacement’. Estimate values for angular distance and angular displacement when the gymnast has completed the double somersault. [4]

(b).

Define the term ‘centre of mass’. Describe how a performer applies an eccentric force to a ball and explain its effect. [5]

2(a).

Define the analogue of Newton’s First Law of Motion. Explain how a figure skater controls angular velocity when performing a multiple spin about the longitudinal axis. [6]

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(b).

Fig. 1 represents the flight paths of three different projectiles in sport.

represents the flight path of a tennis ball with topspin

represents the flight path of a shot in athletics

represents the flight path of a javelin in athletics Fig. 1

Draw a free body diagram for each projectile showing all the forces acting during flight. Explain the shape of the flight path for each of the projectiles. [20]

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3(a).

Fig. 3 shows the forces acting on a fast moving shuttle during flight.

Fig. 3

Using the information in Fig. 3, draw a parallelogram of forces diagram to show how to resolve the net force acting on a fast moving shuttle during this phase of its flight. Explain how this net force causes a deviation in the normal flight path of a fast moving shuttle. [5]

(b).

Fig. 4 shows the speed of a swimmer at set times after pushing off from the side of a pool at the start of a race. Time / secs Speed / ms-1

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0.5

3.0

1.0

2.5

1.5

2.0

2.5

2.0

3.0

2.0 Page 5 of 35

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3.5

2.0

4.0

2.0 Fig. 4

Sketch a graph of speed against time for the swimmer. The mass of the swimmer is 80 kg. For the first 0.5 seconds after pushing off from the side of the pool, calculate:  

the average acceleration of the swimmer the average net force acting on the swimmer.

Use Newton’s Laws of Motion to help explain the shape of the graph. Analyse the methods used by performers to minimise air resistance, fluid friction or drag. [20]

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Using practical examples, describe the use of the three axes of rotation in sport. Explain how rotation is initiated by a performer. Describe the angular analogue of Newton’s First Law of Motion and use it to explain how a high board diver performing somersaults uses their body position to maximise performance during the following phases of the dive:   

Take off from the diving board During flight Just before entry into the water. [20]

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Define linear motion and explain how linear motion is created.

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[2]

Identify two factors that affect the horizontal distance travelled by a projectile.

[2]

Table 1 shows the time in seconds that a 100m sprinter covered each 10 metre section of a race. Table 1 Distance (m)

Time taken (s)

0–10m

1.86

10–20m

1.03

20–30m

0.92

30–40m

0.88

40–50m

0.88

50–60m

0.83

60–70m

0.83

70–80m

0.86

80–90m

0.85

90–100m

0.85

Total time

9.79 seconds

Using the data in the table, calculate the following to two decimal places, showing your working: i.

Average velocity between 0–10m.

[2]

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ii.

Average acceleration between 0â&#x20AC;&#x201C;10m.

[2]

iii.

Average velocity during the race.

[1]

A basketball player jumps vertically during a match. Draw a free body diagram to show the vertical forces acting on the basketball player during take off. Explain the relationship between the size of the vertical forces and their impact on the size of the resulting vertical jump. [5]

Sketch a free body diagram showing all the forces acting on a table tennis ball with backspin during flight. Explain how backspin causes a deviation in the flight path and the bounce of a table tennis ball. ÂŠ OCR 2017. You may photocopy this page.

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Critically evaluate the use of backspin in sport. [20]

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10(a).

Fig. 3 shows a gymnast performing a back somersault. Fig. 3

Explain how angular velocity is controlled by the gymnast during take-off, flight and landing.

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[6]

(b).

A footballer taking a free kick may apply sidespin to the ball to make it swerve. Draw and label an airflow diagram of the ball in flight. Explain how spin causes the flight path of the ball to deviate.

[5]

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11.

A 4 Ă&#x2014; 400 metre relay race takes place on a standard 400 metre track and the baton is correctly passed between the four runners. Calculate the distance covered and displacement of the baton during the race.

[2]

12.

In order to achieve success in swimming, performers must have good technique and excellent fitness. They must also minimise the effect of drag in the water. Identify and evaluate ways that a swimmer can minimise drag.

[6]

END OF QUESTION paper

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Mark scheme Mark Question

Answer/Indicative content

Guidance s Pts 2 and 4 units must be stated Examiner’s Comments

Definitions

Some candidates could

4 marks for

define both angular

1. (angular distance)

The angle through which a body has rotated (about an axis) in moving from the first position to the second.

2. (estimation)

4Π rads / 12.5 rads / 720°/2 revs

3. (angular displacement)

The shortest change in angular position / smallest angle through which a body can rotate to reach the second position from the first position.

4. (estimation)

0 rads / 0°/0 revs

distance and angular displacement accurately. Others only had a vague 4

idea and a few left this question unanswered. The values estimated were generally well done with units included as is the convention. Some candidates did not include the appropriate units and therefore could not score the marks available.

Definition centre of mass (sub max 1)

Is the position on a body through which it is balanced in 1. (centre all directions or the point at which the mass of a body is of mass) said to be concentrated / said to act

Examiner’s Comments

Centre of mass was generally well defined Description of performer applying eccentric force (sub max 2)

and the better candidates

2. (eccentric force)

Is an off centre force / moment of force / torque

Force applied outside the centre of mass of the ball

could describe how a 5

performer applies an eccentric force to a ball. Some candidates did not then go on to explain its effect and therefore did not have access to the

Explanation its effect (sub max 2)

full range of marks.

4. (effect)

Creates spin / angular motion / angular momentum / rotation

Candidates are reminded

Causes swerve / dip / lift / deviation in flight

each question.

Total

to attempt all aspects of

Define the analogue of Newton’s First Law of Motion.

Graphs may show pt 5

Explain how a figure skater controls angular velocity when performing a multiple spin about the

and 7 with correct axes

longitudinal axis. (6)

Examiner’s Comments

Definition (sub max 1)

labelled

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A body will (rotate) with constant angular momentum 1. (Analogue unless acted upon by an external torque / moment / of N1) angular force.

Many candidates were able to define the analogue of Newton’s

Explanation (sub max 5)

2. (Angular momentum)

Angular momentum = Moment of Inertia x Angular Velocity / AM = Iω

3. (Start)

Angular momentum is generated at the start when an external torque / off centre force is applied to the skater by the ice.

First Law of Motion. This topic area includes definitions that are often asked for in the examination and many centres are aware that definitions are often

5. (Start)

Low angular velocity

6. (During)

Narrower body position or arms / legs brought in to reduce MI

and raise candidates’

Increases angular velocity / spins faster

succinctly and accurately

7. (During)

required by examiners

awareness of the need to

define certain terms

8. (Just before stopping)

Arms / legs out to increase MI

9. (Just before stopping)

Reduce angular velocity to prevent over rotation when stopping / land safely / more controlled finish

identified in the specification. Only the very best candidates were able to give a full explanation (worth five marks) of how a figure skater controls angular velocity when performing a multiple spin about the longitudinal axis. Many candidates indicated that the movements of arms and / or legs can affect moment of inertia, but some responses lacked the detail necessary to score high marks.

(d)* Levels of Response : Draw a free body diagram…..Explain the shape of the flight path for each of the projectiles……

Level 4 (18 – 20 marks) A comprehensive answer:

  

detailed knowledge & excellent understanding

At Level 4 responses

detailed analysis and excellent critical evaluation

are likely to include:

well–argued, independent opinion and judgements which are well supported by relevant practical examples

 



Explanation of

very accurate use of technical and specialist vocabulary

the three flight

high standard of written communication throughout.

paths shows excellent understanding



Level 3 (13 – 17 marks) A competent answer:

Detailed knowledge and excellent

 

good knowledge and clear understanding

understanding

good analysis and critical evaluation

of Magnus and

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

independent opinions and judgements will be present but may not always be supported by relevant

Bernoulli effect

practical examples

 

demonstrated

generally accurate use of technical and specialist vocabulary



written communication is generally fluent with few errors.

accurate free body diagrams showing all forces acting

Level 2 (8 – 12 marks)

during flight



A limited answer:

Excellent understanding

    

limited knowledge and understanding

some evidence of analysis and critical evaluation

consequences

opinion and judgement given but often unsupported by relevant practical examples

of forces for

technical and specialist vocabulary used with limited success

three flight

written communication lacks fluency and contains errors.

paths.

Level 1 (0 – 7 marks)

At Level 3 responses

A basic answer:

are likely to include:

    



basic knowledge and little understanding

Explanation of

little relevant analysis or critical evaluation

the three flight

little or no attempt to give opinion or judgement

paths shows a

little or no attempt to use technical and specialist vocabulary

clear

errors in written communication will be intrusive.

understanding



good knowledge and clear understanding

Indicative Content:

of Magnus and

(Draw a free body diagram…..Explain the shape of the flight path for each of the projectiles……)

Bernoulli effect demonstrated



Free Body Diagram X (Ball with topspin)

Free body diagrams show all forces but there may be some inaccuracies



clear understanding of consequences

Free Body Diagram Y (Shot)

of forces for at least two of the flight paths.

At Level 2 responses are likely to include:



Explanation of the flight paths shows limited knowledge and / or

Free Body Diagram Z (Javelin)

understanding

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

Limited knowledge and understanding of Magnus and Bernoulli demonstrated



free body diagrams attempted but incomplete or

Free body diagrams

with inaccuracies

1. (FBD X – ball with topspin)

Weight acting downwards from CM

Air resistance acting from CM opposite direction of motion



understanding

Magnus force acting downwards from CM / surface of ball

4. (FBD Y – shot)

Weight acting downwards from CM

Air resistance acting from CM opposite direction of motion and significantly smaller than weight.

of consequences of forces

At Level 1 responses are likely to include:



6. (FBD Z – javelin) Weight acting downwards from CM 7.

Explanation of the flight path(s) shows

Air resistance acting from CM opposite direction of motion

basic knowledge and

/ or

Explanation of FP

Ball with topspin

understanding



Top surface of ball is travelling in opposite direction to airflow. 9. (Top of the ball)

limited



free body diagrams



Air travels shorter distance over top of ball.

An attempt at

basic knowledge and / or understanding

Air decelerates / travels slower

of consequence

10.

11. (Underneath the ball)



Creates high pressure above ball

of forces

Bottom surface of ball is travelling in same direction as airflow. Examiner’s Comments



Air travels further underneath ball. This was well-answered

Air accelerates / travels faster 12.

by some candidates. The best candidates drew



Creates low pressure underneath ball.

clear and well-labelled diagrams with all the

High to low pressure gradient 13.

 

Causes downwards force to act on ball Aiding the effect of weight.

forces shown acting on the projectile during flight. Many centres have obviously ensured that these candidates practice this sort of question

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Causes ball to dip in flight

regularly. Some candidates drew unclear

14. (Consequence)

 

Shortening flight path of ball. Causes non parabolic / asymmetrical flight path

diagrams with illegible labels and consequently scored few marks. The explanations of the shape of the flight path for each

Weight is dominant force. 15. (Shot – forces)



projectile by the top candidates revealed

As mass of shot is big.

excellent knowledge and understanding with most

Air resistance is negligible 16.

showing a good understanding of the



As shot travels slowly.

Magnus and Bernoulli effects. The best

17. (Consequence)

candidates wrote clearly

Shot follows a (nearly) parabolic / symmetrical flight path

about the consequences of the flight path of

Javelin assumes an aerofoil shape

projectiles for example that the javelin could

18. Javelin



Most efficient shape that can generate lift while at the same time minimise air resistance.

hang in flight as a consequence of the Bernoulli effect.

Creates an angle of attack to airflow / the horizontal 19.



Lift force will increase as angle of attack increases up to a certain point / about 17degrees.

Air travels further over the top of the javelin 20.



So air travels faster over the top

This creates a low pressure over the top 

21. 

Thus creating a high to low pressure gradient upwards. Creating a lift force / Bernoulli effect upwards.

Causing the javelin to hang in flight 22. (Consequence)

 

Increasing the distance travelled Reducing the effect of weight.

Total

26 Sub max 3 for diagram

Sub max 3 marks for diagram

5 Sub max 3 for

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explanation Examiner’s Comments

Most candidates could use the diagram to draw a parallelogram of forces to show how to resolve the net force. Candidates described the flight path of the fast moving shuttle but often failed to explain why the path was shortened. This may have indicated a lack of required knowledge or a misunderstanding of the question. Some candidates misinterpreted the question and explained the flight path Diagram must show

rather than explaining the

1. (Forces)

Air resistance longer than Weight

2. (Parallelogram)

Parallelogram using forces in 1 (dotted lines)

3. (Resultant / net force)

Resultant or net force shown correctly.

effect of resultant force.

Explanation of how net force causes deviation in Flight Path. (Sub max 3)

Shuttle decelerates 4. or follows a non-parabolic (Description) or asymmetric flight path Resultant / net force is (nearly) same direction as air 5. resistance / closest to air resistance / opposite (Explanation) direction of motion 6. Resultant / net force shows direction / magnitude (Explanation) (size) of acceleration of shuttle 

(d)* Levels of Response Level 4 (18–20 marks) A comprehensive answer:  b

 

relevant

At level 4 answers are likely to show:  



Accurate sketching of graph. Correct calculations using appropriate formulae and units. Detailed understanding and application of Newton’s Laws in interpreting the speed / time graph.

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Give KU for

knowledge points (usually main headings) 20



Give DEV for relevant development points (usually bullet points)



Give EG for relevant

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

very accurate use of technical and specialist vocabulary high standard of written communication throughout.



Detailed analysis of a wide range of methods used to overcome air resistance / fluid friction with relevant sporting examples.

practical examples



Always indicate the Level at the base of the answer

Level 3 (13–17 marks) A competent answer:   



good knowledge and clear understanding good analysis and critical evaluation independent opinions and judgements will be present but may not always be supported by relevant practical examples generally accurate use of technical and specialist vocabulary written communication is generally fluent with few errors.

At level 3 answers are likely to show: 



Accurate sketching of graph and correct calculations but answer may not always have either the appropriate formula or units. Good understanding and application of Newton’s Laws but answer may not always be accurate in interpreting the speed / time graph. Good analysis of a range of methods used to overcome air resistance / fluid friction with some relevant sporting examples.

(L1,L2, L3 or L4)



Do not be limited by the indicative content give credit for other relevant points or developments .



Do not give credit to irrelevant material

Examiner’s Comments

Most candidates showed

Level 2 (8–12 marks) A limited answer:

At level 2 answers are likely to show:

an appropriate sketch graph of speed against time for the swimmer, but

  



limited knowledge and understanding some evidence of analysis and critical evaluation opinion and judgement given but often unsupported by relevant practical examples technical and specialist vocabulary used with limited success written communication lacks fluency and contains errors.



 



Good shape of graph but axes may not be fully labelled. Some aspects of calculations correct. Some understanding of Newton’s Laws but limited application to shape of the graph. Some methods identified that overcome air resistance / fluid friction with a few sporting examples.

some candidates were unable to do the calculations related to the average acceleration of the swimmer and the average net force acting on the swimmer. A significant minority did not use the appropriate units for their calculations. Most candidates gave an accurate account of Newton’s Laws of Motion to help their explanation of the graph, although many simply focussed on

Level 1 (0–7 marks) A basic answer:

At level 1 answers are likely to show:

one law for each stage of the graph or were too superficial in their

 

basic knowledge and little understanding little relevant analysis or critical evaluation



Show some correct aspects of the graph or some correct aspects of calculations.

explanations. Candidates often gave an analysis that was too brief and under-developed to show appropriate methods

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 



little or no attempt to give opinion or judgement little or no attempt to use technical and specialist vocabulary errors in written communication will be intrusive.



Identify some of Newton’s Laws but show limited application. Identify some methods that overcome resistance or give a few sporting examples.

used by performers to minimise air resistance, fluid friction and drag. The better candidates analysed well and applied theory to practice throughout.

Indicative Content: Reference to question

Speed / time graph

Accept a sketch graph

Correct axes 1. (Speed / time graph)

2. (Acceleration)

 

correct plotting correct shape

Acceleration = final-initial velocity / time or finalinitial speed / time a = v – u / t or a = 3.0 – 0 / 0.5 

a = 6ms-2 (m / s / s or m.s2)

F = ma or F = 80(kg)x6(ms-2) 3. (Net force)



480 Newtons (N)

Law of Inertia 

4. (Newton 1)

An object will remain at rest or move with uniform motion / constant velocity / constant speed unless acted upon by an external / unbalanced force.

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Law of acceleration or momentum 

5. ( Newton 2)

The acceleration / rate of change in momentum of an object is directly proportional to the (net) force acting upon the object and acts in the same direction as the (net) force (applied).

Law of Reaction 6. (Newton 3)



For every action (force applied) there is an equal and opposite reaction (force).

shows acceleration 

7. (1st part of graph) 

Newton 1 suggests that because there is an acceleration there must be an external / unbalanced force acting on the swimmer / swimmer has generated / applied a force Newton 2 suggests that the acceleration is large due to a large (net) force acting on / generated by the swimmer.

shows net forward force acting on swimmer 

(1st

8. part of graph)

Newton 3 suggests that the swimmer pushes/(applies an action force)backwards against the wall and the wall applies an equal and forwards (reaction) force on the swimmer.

shows deceleration of swimmer 

9. (2nd part of graph)

 

Newton 2 suggests that a (net) force must be acting against the swimmer / opposite direction. Fluid friction / Water resistance Newton 1 suggests that there must be an external / unbalanced force acting on the swimmer

shows constant speed 

10. (3rd part of the graph)



Newton 1 suggests that all forces are balanced as the swimmer is moving with constant velocity / speed. Newton 2 suggests the net force acting on the swimmer is zero as there is no acceleration

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Streamlining 

11. (Overcoming air resistance / fluid friction / drag)



Creating smooth flow around the performer / reducing (turbulent) drag. Reducing profile drag / turbulence behind the performer

Making surface of performer smoother  

12. (clothing)

Use of special swimwear / hats / shaving Use of special / lycra suits for skiers or eq.

Reducing friction between air / water and performer. 

13. (density)



Reduction in density of water in swimming pools Performing at altitude

Reducing frontal / forward cross sectional area of performer 14. (frontal crosssection)

 

Lying flatter in the water Maintaining narrow body shape / tuck shape in skiing / cycling or eq.

Changing shape / ‘tear drop’ shape / ‘aerofoil’ shape / changing action. 

15. (shape)



Dolphin action been added to all techniques not just butterfly / bike design Helmets in cycling / speed skiing

Reducing surface effects / wave drag 16. (surface effects)



Swimming underwater as far as possible / as far as rules allow.

Reducing speed / velocity 17. (speed)



Not beneficial to performance / must reduce AR / FF in other ways

Total



relevant

Levels of Response 4

Level 4 (18-20 marks) A comprehensive answer:

Give KU for

At level 4 answers are likely to show:

knowledge points (usually main headings)

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   



detailed knowledge excellent understanding detailed analysis and excellent critical evaluation well-argued, independent opinion and judgements which are well supported by relevant practical examples very accurate use of technical and specialist vocabulary high standard of written communication throughout.



Detailed description of three axes of rotation with relevant sporting examples. Detailed explanation of how rotation is generated. Better candidates may illustrate their answer with sporting example. Detailed understanding of the analogue of Newton 1 and its application to a somersault. Detailed explanation of how angular momentum, moment of inertia and angular velocity vary during the three stages of somersaulting.

Give DEV for relevant development points (usually bullet points)



Give EG for relevant practical examples



Always indicate the Level at the base of the answer (L1,L2, L3 or L4)

Do not be limited by the indicative content give credit for other relevant points or developments.

Level 3 (13-17 marks) A competent answer:   



At level 3 answers are likely to show: 

 



Do not give credit to irrelevant

Good description of three axes of rotation with some sporting examples at the top of this band. Good explanation of how rotation is generated. Good understanding of the analogue of Newton 1 and its application to a somersault. Good explanation of how angular momentum, moment of inertia and angular velocity vary during the three stages of somersaulting.

material

Examiner’s Comments

This was well answered by many candidates. High scoring candidates ensured that they covered each aspect of the question and planned their time accordingly. Some made useful headings that helped them focus on each aspect of the question.

Level 2 (8-12 marks) A limited answer:

At level 2 answers are likely to show: 

  

limited knowledge and understanding some evidence of analysis and critical evaluation opinion and judgement given but often unsupported by relevant practical examples

  

Identification of at least two axes of rotation with sporting examples. Description of how rotation is generated. Some understanding of the analogue of Newton 1. Limited explanation of how angular momentum, moment of inertia and Page 25 of 35

Most could describe the three axes of rotation, using practical examples, often from athletics or gymnastics. The explanations related to how rotation is initiated were less well done by many candidates, with some simply leaving this aspect of the question unanswered. The better candidates then went on to describe well the

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

technical and specialist vocabulary used with limited success written communication lacks fluency and contains errors.

angular velocity vary during the three stages of somersaulting.

angular analogue of Newton’s First Law of Motion and used it well to explain the scenario given in the question. Lower scoring candidates did not address the different phases of the

Level 1 (0 – 7 marks) A basic answer:    



dive - again indicating that some candidates do

At level 1 answers are likely to basic knowledge and little show: understanding little relevant analysis or  Identify an axis of rotation. critical evaluation  Have a basic understanding little or no attempt to give of how rotation is opinion or judgement generated. little or no attempt to use  Identification of angular technical and specialist momentum, moment of vocabulary inertia and angular velocity. errors in written communication will be intrusive.

not read each question carefully enough.

  

Take off from the diving board During flight Just before entry into the water.

Indicative Content: Using practical examples, describe the use of the three axes of rotation in sport.

Longitudinal axis 1. (Axes of rotation)

 

Head to toe Eg Spin in a discus turn

Transverse axis 2.

 

Side to side Eg Somersault in trampolining

Frontal axis 3. 

Front to back

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

Eg Cartwheel in gymnastics

Explain how rotation is initiated by a performer. Off centre / eccentric force 

4. (Initiation of rotation)



(Reaction) Force applied outside axis of rotation / centre of mass Eg diver leans backwards at take off in a backward somersault / high board diver leans forwards at take off to clear the board Free body diagram showing R force from point of contact passing in front or behind the centre of mass

Gives Moment of Force / Torque / couple 5.

 

Force x distance from fulcrum Gives object Angular Momentum

Describe the angular analogue of Newton’s First Law of Motion and use it to explain how a high board diver performing somersaults uses their body position to maximise performance during the following phases of the dive: The angular momentum of a rotating body will remain constant unless acted upon by an external torque / moment of force / eccentric force 

6. (Analogue of N1)  

Also known as the Law of Conservation of Angular Momentum Eg the diver will not rotate until a torque / moment of force is applied e.g. the diver will continue to rotate with constant angular momentum, until acted upon by an external torque / moment of force…

Angular momentum refers to the amount / quantity of angular motion a (rotating) body possesses / is a measure of angular motion. 

  

Depends on its moment of inertia and angular velocity. AM = moment of inertia x angular velocity / Iω Moment of inertia is resistance of an object to rotation / rotational equivalent of inertia. Depends on distribution of mass from the axis of rotation

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

Angular velocity is the rate of change of angular displacement / angular displacement / time (rads.s) / rate of spin.

MI is high 8. (Take off from diving board)

 

Divers mass is distributed away from axis of rotation / centre of mass Eg Diver is in a straight body position at take off

(Angular Momentum) given to diver about transverse axis of rotation. 



Reaction force from feet acts outside of the centre of mass of the diver. Shown through diagram

Angular velocity is low  

10.

Rate of spin is low. increases control going into the rotation / somersault

MI is reduced 11. (During flight)

 

Diver’s mass is brought closer to axis of rotation Eg diver tucks up

Angular velocity / rate of spin increases 

12. 

Because Angular Momentum is conserved / remains constant Eg This means diver can perform more somersaults during dive.

MI is increased 13. (Just before entry in to the water)

  

To increase resistance to rotation Divers mass is distributed away from axis of rotation / centre of mass Eg Diver straightens body

Angular velocity is reduced 14.

 

Prevents over rotation on entry Eg Diver’s entry is safer / scores better

Total

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Two marks from: 2

 

definition – movement in a straight line

(AO1 )

creation - direct force / force applied through centre of mass

Total

Two marks from:

   

height of release

(AO1

speed / velocity of release

)

angle of release air resistance / shape of object / spin of the object

Total

Two marks for: 2 7

 

(AO2

velocity = Distance / time or 10/1.86

)

5.38m / s or ms-1

Must show units for full marks.

Two marks for: 2

 

(AO2

acceleration = change in velocity / time or v-u / t or 5.38/1.86

)

2.89m / s2 or ms-2

Two marks from:



(AO2 Average velocity = 100/9.79 = 10.21m / s or ms-1

)

Total

Must show units for full marks.

Allow error carried forward in calculations.

5 marks for 5 of

2 marks sub max for

2 marks max for diagram

diagram

Free Body Diagram to show vertical forces acting on basketball player during take off

3 marks sub max for explanation Examiner’s Comments

Many candidates showed accurate free body 8

diagrams but a minority were unclear in their drawings. Only the best candidates then gave three valid points related to explaining the relationship between size

1. (Weight)

of vertical forces and their

Weight downwards from CM.

impact on the size of the

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resulting vertical jump.

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Explain the relationship between size of vertical forces and their impact on the size of the resulting vertical jump (3 marks sub-max)

3. R > W means there is an unbalanced force acting on (Relationship) basketballer. 4. R > W means there is a net / upward force. (Relationship) 5. (Impact)

Therefore there is an upwards acceleration.

6. (Impact)

The bigger the reaction force, the greater the net upward force / the greater the upwards acceleration / the greater the height achieved by the basketball player.

Total

(d)* Levels of Response At level 4 answers are likely to show: Level 4 (18-20 marks) A comprehensive answer:   



detailed knowledge & excellent understanding detailed analysis and excellent critical evaluation well–argued, independent opinion and judgements which are well supported by relevant practical examples very accurate use of technical and specialist vocabulary high standard of written communication throughout.

 



Accurate FBD showing W, AR and MF. Detailed explanation of how backspin causes the deviation in the flight path of the ball. Detailed explanation of how backspin causes the deviation in the bounce of the ball. Advantages and disadvantages of the use backspin in sport covering both the flight path and the bounce. Good use of practical examples in the critical evaluation.

Examiner’s Comments

This was well answered by many candidates who were able to accurately sketch a free body diagram clearly showing all the forces acting on the table tennis ball with backspin. These successful candidates then clearly explained how backspin causes deviation both in the flight path and the bounce of 20

the ball. The best candidates gave an excellent critical evaluation of the use of backspin in sport using a range of practical

Level 3 (13-17 marks) A competent answer:   

good knowledge and clear understanding good analysis and critical evaluation independent opinions and judgements will be present but may not always be supported by relevant practical examples

At level 3 answers are likely to show:

examples - often using tennis, football and golf as relevant sports.

 



FBD accurately showing W and AR. Good explanation of how backspin causes the deviation in the flight path of the ball. Good explanation of how backspin causes the deviation in the bounce of the ball. Page 30 of 35

Those that scored less well did not address all aspects of the question, for example explaining how backspin affects the flight path but omitting the bounce of the ball. Others did not include a critical evaluation or who were too descriptive in this part of their answer and not

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

generally accurate use of technical and specialist vocabulary written communication is generally fluent with few errors.



Advantages and disadvantages of the use backspin in sport covering either the flight path or the bounce. Some use of practical examples in the critical evaluation.

identifying clearly the advantages and disadvantages of the backspin.

At Level 2 answers are likely to show: Level 2 (8-12 marks) A limited answer:   



Level 1 (1–7 marks) A basic answer:    



basic knowledge and little understanding little relevant analysis or critical evaluation little or no attempt to give opinion or judgement little or no attempt to use technical and specialist vocabulary errors in written communication will be intrusive.

 



FBD showing W and AR. Limited explanation of how backspin causes the deviation in the flight path of the ball. Limited explanation of how backspin causes the deviation in the bounce of the ball. Advantages or disadvantages of the use backspin in sport covering either the flight path or the bounce. Little use of practical examples in the critical evaluation.

At level 1 answers are likely to show:  



An attempt at a FBD. Description of the effect of backspin on the flight path of the ball. Description of the effect of backspin on the bounce of the ball. Little attempt at an evaluation of the use of back spin in sport. Little or no use of practical examples in the critical evaluation.

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Indicative Content: Free body diagram

Acting downwards from CM (centre of mass) 1. (Weight)



Arrow short in length

Acting from CM  

2. (AR)

Opposite direction of motion Larger than W arrow

Acting upwards from CM / surface of ball 3. (Magnus force)



Perpendicular to direction of motion

Explanation of backspin on flight path

Air travels further over the top of the ball (or opp.) 

4. (Air flow)

 

Therefore, air travels faster over the top of the ball Airflow assisted / accelerated by direction of spin Venturi created above the ball

This creates low air pressure over the top of the ball 5. (Air pressure)

6. (Magnus force)



Creating (a high to low) pressure gradient (upwards)

This creates (an additional) force acting upwards on the ball 

Called the Magnus force

Counteracts the force of weight / reduces the effects of W 7. (Effect)

 

Ball hangs in the air / stays in the air for longer Covers greater distance

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Explanation of backspin on the bounce

Surface of ball trying to slide forwards on ground 8. (friction)



Friction acts in opposite direction / backwards

(Resultant / net) force acts backwards 9. (effect)

 

Causes ball to decelerate / slow down / lose momentum Ball ‘sits up’

Evaluation of backspin

Flight path lengthens 10. (flight path lengthens)

 

(advantage) Hit ball further eg drive in golf, goalkick in football (disadvantage) Ball travels too far before landing eg sliced backhand in tennis.

Ball travels slower / hangs in the air (to reach same point) 

11. (slower flight )

  

(advantage) Gives more time to recover before next shot eg defence in table tennis. (advantage) Easier for teammate to control eg long diagonal pass in football (advantage) Ball does not roll as far after landing eg approach shot in golf (disadvantage) gives more time for opponent to intercept / attack eg opponent has time to move in and volley in tennis

Backspin makes ball sit up / stop on landing 

12. (bounce)

 

(advantage) Drop shots with backspin make opponent move further eg tennis. (advantage) Gives more control over ball on landing eg pitch in golf (disadvantage) Easier for an opponent to attack eg tennis

Total

Six marks for:

 1 0

6 (analogue of Newton 1) A body will continue to rotate with constant angular momentum unless acted upon by an external torque / moment (AO1)

   

(3 x AO1,

(momentum) Principle of conservation of angular momentum (AO1) (AM) AM = Iw / angular momentum = moment of inertia x angular velocity(AO1)

3x AO2)

Maximum 3 marks for AO1. Maximum 3 marks for AO2.

(take-off) gymnast generates angular momentum off floor (AO2) (MI) Moment of inertia high as body is extended (AO2)

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     

(AV) therefore angular velocity (w) / rate of spin is low (AO2) (flight - MI) MI is reduced as body is tucked (AO2) (AV) therefore angular velocity / rate of spin increases (AO2) (entry - MI) MI is increased as body is extended (AO2) (AV) therefore angular velocity / rate of spin is reduced (AO2) to prevent over rotation / controlled landing (AO2)

Five marks from:

Sub max 4 if no diagram. Credit points whether 5

given in diagram or

(AO2

)

written below. NB. Diagram below does not show bullet points 2 or 3.

       

airflow arrows in opposite direction to motion of ball wider airflow lines on side away from direction of swerve / narrower on side of direction of swerve higher pressure where airflow lines are wider / lower where lines are narrower direction of spin matches direction of swerve (Effect of swerve is) magnus force / effect caused by pressure gradient from high to low air travels further on low-pressure side of ball / or opposite air travels faster on low-pressure side of ball / or opposite

Total

11 Answer must show correct unit for

Two marks from: 2

1 1

(Distance) = 1600 metres or 1.6km

(Displacement) = 0

distance.

(AO3 Displacement does not

)

need a unit for point 2 to be given Total

2 Do not accept:

Six marks from:

Method of reducing drag 1 2

Evaluation

2. An effective technique as 1. Reduce frontal / forward crossswimmer keeps body as flat as sectional area possible or freestyle stroke

Sub max 3 marks for

(3 x

points for identifying ways

AO2

to minimise drag.

3x AO3)

Sub max 3 marks for evaluation of each way.

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minimises FXSA / hands enter water at same point

3. Streamlining or shape

4. Smooth flow of water around a tear-drop shape/ freestyle very streamlined vs breaststroke less so

5. Reduce surface effects / minimise turbulence / smooth surface

6. Easily done by wearing smooth swimsuits / swim caps or removing body hair / underwater swimming

7. Reduce speed / velocity

8. Not a feasible method as speed is key to success!

Total

ÂŠ OCR 2017. You may photocopy this page.

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