Action and reaction force pairs

Grade 8 Science Worksheet - Building Confidence

Circle the best answer.

1. 1.

   Ari pushes off the pool wall, pushing the wall to the left. Which way does the wall push Ari?

   • To the left
   • It doesn't push, since walls can't move
   • To the right

2. Read this first

   Use this

   Force arrow diagram, one dimension, arrows drawn to scale by size. Box A: person's push on the cart 20 N pointing right. Beside it: lab cart. Box B: cart's push on the person ? pointing left. Beside it: person.

3. 2.

   Jun pushes a lab cart with 20 N. How hard does the cart push back on Jun?

   • 0 N, since a cart can't push
   • 10 N, since the cart is small
   • 40 N, since a person is bigger
   • 20 N

4. Use this

   Force arrow diagram, one dimension, arrows drawn to scale by size. Box A: adult's push on child 60 N pointing left. Beside it: adult. Box B: child's push on adult ? pointing right. Beside it: child.

5. 3.

   Kira and a coach press palms together. The coach pushes with 60 N. How hard does Kira push back?

   • 0 N, since the coach stayed put
   • More than 60 N, since kids push harder
   • 60 N
   • Less than 60 N, since the coach is bigger

6. Use this

   Force arrow diagram, one dimension, arrows drawn to scale by size. Box A: ball on floor 15 N pointing down. Beside it: gym floor. Box B: floor on ball ? pointing up. Beside it: basketball.

7. 4.

   A bouncing basketball pushes the gym floor down with 15 N. How hard does the floor push the ball up, Luz?

   • More, since the floor is bigger
   • 15 N
   • 0 N, since the floor stays still
   • Less, since the ball is lighter
8. 5.

   Milo pushes a heavy classroom door open. The hand pushes on the door. What does the reaction force push on?

   • The hinges
   • The door
   • The hand
   • The floor
9. 6.

   Noah kicks a soccer ball. The foot pushes on the ball. The reaction force acts on which object?

   • The foot
   • The ball
   • The grass
   • The air
10. 7.

    Pia paddles a canoe. The paddle pushes the water backward. What does the reaction force push on?

    • The paddle
    • The shore
    • The water
    • The air

11. Use this

    Force arrow diagram, one dimension, arrows drawn to scale by size.

12. 8.

    Two skaters push apart with 40 N each. Do the two forces cancel, Ren?

    • No, one push is bigger
    • Yes, so neither skater moves
    • No, they act on different skaters
    • Yes, they are equal and opposite
13. 9.

    Tala pushes a ball with 5 N, and the ball pushes back with 5 N. Why does the ball still roll?

    • The hand's push comes first
    • The forces cancel, so it shouldn't
    • They act on different objects
    • The ball's push is weaker
14. 10.

    Zee tugs a cart with a rope. The rope pulls the cart; the cart pulls the rope back. Do these cancel?

    • No, the cart's pull is bigger
    • Yes, they are the same size
    • No, they act on different objects
    • Yes, so the cart can't move