Science
Science
FORCES AND MOTION
WEEK 3 DISPLACEMENT-TIME GRAPHS
VELOCITY-TIME GRAPHS
NEWTON’S LAWS OF MOTION
Displacement is how far an object is from its original
Velocity is speed in a fixed direction. Velocity-time
NEWTON’S 1ST LAW
position, so a displacement-time graph shows how
graphs show how the velocity of an object varies
this changes as time passes during a journey (or
during the time of a journey.
Newton’s 1st Law means UNBALANCED FORCES cause ACCELERATION (note - this is not a statement of Newton’s 1st Law, this is just how it works.) If the object is originally AT REST (stopped) it will SPEED UP FORWARDS or BACKWARDS. If the object is already moving with a CONSTANT VELOCITY it will SPEED UP in the direction it’s moving or SLOW DOWN. (It might even start to go backwards if
whilst the object is stopped).
Velocity can be a negative value if an object is
Using the graph we can work out the speed of an
travelling in the opposite direction to the one
object by looking at the steepness of the line and
chosen, for example if you choose ‘upwards’ as
finding the gradient (how far up divided by how
the positive direction then ‘downwards velocities’
far along that section goes).
would be negative.
the force acts for long enough!)
Like with displacement graphs, the gradient of
1.
1.
There is a more suitable physics word for
the line can tell us something – in this case the
‘getting faster’. What is it?
acceleration.
State Newton’s 1st law of Motion.
Acceleration = change in velocity/time
NEWTON’S 2ND LAW
HIGHER ONLY On higher exams you might be asked to determine the distance an object has travelled on the journey, which is the area under the graph up to that point. The area can be split into rectangles and triangles,
Newton’s 2nd Law is the equation F = m x a, which tells us how much force is needed to make a mass accelerate at a certain rate. F = m x a a = F/m m = F/a 1N of force on 1kg of mass causes 1m/s² of acceleration. 2.
Calculate the acceleration on this block if all the forces are shown.
and the usual maths rules used to calculate them. You might also, as with displacement graphs, be asked to find an acceleration at a certain point on a curve using the gradient of a tangent.
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YEAR 10 S UMMER BO O KL ET
Delta Academies Trust
NEWTON’S 3RD LAW Newton’s 3rd Law is that every force or action has an equal, opposite reaction force. What this means is that when one object causes a force on another object, an equal force acts back on the first object.
YEA R 10 SUM M ER B OOK L ET
Delta Academies Trust
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