Action and reaction force pairs

Grade 8 Science Worksheet - Building Confidence

Circle the best answer.

1. Read this first

   Use this

   Force arrow diagram, one dimension, arrows drawn to scale by size. Box A: skater on rail 30 N pointing left. Beside it: the rink rail. Box B: rail on skater ? pointing ?. Beside it: the skater.

2. 1.

   At the rink, Bo pushes the rail to the left with 30 N. Which way does the rail push Bo?

   • To the right
   • To the left
   • It waits until the rail moves
3. 2.

   Force arrow diagram, one dimension, arrows drawn to scale by size. Esme presses a hand on the classroom wall, pushing right. Which way does the wall push the hand?

   • To the right
   • To the left
   • To the left, a moment later

4. 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.

5. 3.

   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
   • 40 N, since a person is bigger
   • 20 N
   • 10 N, since the cart is small

6. 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.

7. 4.

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

8. 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.

9. 5.

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

   • 15 N
   • More, since the floor is bigger
   • Less, since the ball is lighter
   • 0 N, since the floor stays still
10. 6.

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

    • The door
    • The floor
    • The hinges
    • The hand
11. 7.

    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
12. 8.

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

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

13. Use this

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

14. 9.

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

    • Yes, so neither skater moves
    • No, one push is bigger
    • No, they act on different skaters
    • Yes, they are equal and opposite
15. 10.

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

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