10 minute read
Unit 9 – Forces and Motion
9Forces and Motion
What are pushes and pulls? What can pushes and pulls do?
In this chapter you will ...
• describe force.
• distinguish between pushes and pulls. • identify pushes and pulls in everyday life. • identify forces in nature. • discover how forces can affect motion.
Go Online!
Access interactive content relating to this topic on the NGScience website.
ngscience.com
How do forces affect motion?
AB Activity 9.1
What Is a Force?
What things can you see in the pictures? How are the things moving? What causes them to move?
The things you see are moving because of forces.
A force is a push or a pull.
Which are pushes? Which are pulls?
Try This!
Walk around your schoolyard at lunch time.
What things are moving? What causes them to move?
A push is when you press something away from you. Ethan is using a push force.
A pull is when you tug something closer to you. Jordan is using a pull force.
What happens to the car when it is pushed and pulled?
Try This!
Tie a piece of string to a toy car. Pull on the string. Push the car. What do you observe?
You use a push when you throw, hit or kick a ball.
You use a push when you jump in the air. What are some other ways we use pushes?
How is the girl using a push force?
You use a pull when you drag a sled, climb a rope or rake some leaves.
What is causing the sled to move?
AB Activity 9.2
Think Deeply
When you pick up your school bag, do you use a push or a pull?
Go Online!
Watch a video on pushes and pulls on the NGScience website. QuickCode: Z4Z6
What are some other times you use a pull?
Using Forces
Every day you use forces to make things move in different ways. You use forces when you: • Brush your teeth. • Get dressed. • Open or close a door. • Write, draw or paint. • Pick up your schoolbag. • Exercise and play.
What forces do you use when you ride a bicycle?
What are some other ways you use forces in daily life?
Do you use pushes, pulls or both? What do the forces do?
AB Activity 9.3
Try This!
Act out sweeping with a broom with a partner. How does the broom move? Do you use pushes, pulls or both?
Go Online!
Watch a video showing how things move on the NGScience website. QuickCode: K8J8
How Things Move
Forces make things move in different ways. When you bowl a bowling ball, it moves in a straight line. On a swing, you move back and forth. On a see-saw, you move up and down.
A carousel moves round and round.
Things can move slow or fast. You move slowly when you walk. You move faster when you run.
What other ways can you tell how things move?
AB Activities 9.4 – 9.6
Think of all the ways forces move things in a playground. Which are pushes? Which are pulls?
Forces in Nature
Forces in nature cause things to move.
Wind is causing the sailboats to move.
Engineer It!
Design and build your own sailboat that will move in water!
Moving water pushes the kayak down the river. It pushes a surfer along a wave. Wind and moving water are forces in nature.
What causes the windmill and leaves to move?
Amazing Fact!
People can use the force of moving water and wind to make electricity!
AB Activity 9.7
Force and Movement
The movement of an object is called its motion.
Forces can start, stop and change the motion of an object.
How does the movement of a ball change during a game of tennis?
Go Online!
Watch sports in action on the NGScience website. Describe how forces affect motion. QuickCode: U4P4
Start and Stop
When you pull on the string of a balloon, you start it moving.
Amazing Fact!
During a strongman competition, competitors use pushes and pulls to move a truck!
When you use a push to throw a ball, it starts moving.
A force can start an object moving.
What force does the girl use to start moving on her scooter?
The push force of a kick causes the football to start moving. When the goalkeeper catches the ball, he uses a push force to stop the moving ball.
A force can stop a moving object.
In what other sports do you use a push force to stop a ball?
What are some examples where a force is used to stop a moving object? Are the forces pushes or pulls?
Engineer It!
Find a sloped surface in your school. Roll a ball down the slope. With your friends, design something to stop the ball from moving.
Fast and Slow
Take a toy car and give it a soft push. Try again using a hard push. What do you notice about the motion of the car?
Forces can make things move at different speeds.
When you use a soft push, the toy car moves slowly.
When you use a hard push, the toy car moves faster.
How do hard and soft pushes affect the way a cyclist moves?
Changing Direction
An object moves in the direction it is pushed or pulled.
When you throw a basketball, it moves in the direction you push it. You can change the direction the ball is moving by pushing it in a different direction.
Forces can change the direction of a moving object.
How does the direction of a ball change during a basketball game?
Go Online!
Go to the NGScience website to watch the ways forces make a ball move during a game of basketball. QuickCode: U3S4
Speed Up and Slow Down
When the father pushes the boy, he will go faster.
A force can cause a moving object to speed up.
When the cyclist squeezes the brakes, the bicycle slows down.
A force can cause a moving object to slow down.
AB Activities 9.8 – 9.9
Go Online!
Observe the different ways forces make things move on the NGScience website. QuickCode: S7C8
Engineer It!
As a class, design and build a maze for a ball. Think about how forces will guide the ball through the maze.
Science Words
force push pull motion change direction speed up slow down
Review
1. What is a force?
2. True or false. (a) A pull is when you press something away. (b) A pull is when you tug something closer. 3. Choose a word to label the type of force.
pull push
(a) (b)
4. Tell two ways you use a push force. 5. Tell two ways you use a pull force. 6. Name an activity that uses pushes and pulls. 7. List two forces in nature.
8. What will happen when Blake pedals harder?
(a) He will slow down. (b) He will stop. (c) He will speed up. 9. What will happen when Halle hits the ball?
(a) The ball will stop. (b) The ball will change direction. (c) The ball will start moving.
In the Field
How much force does it take to push a spacecraft into space? This is one of the challenges of an aerospace engineer!
An aerospace engineer researches, designs and tests rockets that carry objects into space.
