Newton's third law: force pairs
Grade 11 Science Worksheet - Challenge Me
Circle the best answer, or write your answer on the line.
A 1.5 kg cart at 2 m/s hits a 0.5 kg cart at rest and they stick. The contact lasts 0.1 s. What average force acts on the 0.5 kg cart, Ari?
A 2 kg cart at 3 m/s hits a 1 kg cart at rest and they stick. The contact lasts 0.05 s. What average force acts on the 1 kg cart, Bo?
A 0.8 kg cart at 1.5 m/s hits a 1.2 kg cart at rest and they stick. The contact lasts 0.2 s. What average force acts on the 1.2 kg cart, Esme?
The contact lasts 0.050 s. Using the table, what average force does each cart feel during the contact, Jun?
- 25 N on cart B and 12.5 N on cart A, since A has half the mass
- 25 N on each cart, in opposite directions
- 0 N on each cart, since the system's total momentum is unchanged
- 50 N on cart A and 25 N on cart B, since A changed speed more
A cart's momentum changes by 5 kg·m/s against a spring in 0.10 s. A softer spring takes 0.20 s. What happens to the forces, Kira?
- Both forces stay at 50 N, since the momentum change is the same
- Both forces double, from 50 N to 100 N, since the time doubled
- The cart's force halves, but the spring's force stays at 50 N
- The cart's force and the spring's force both fall from 50 N to 25 N
The two sensors do not give identical readings in any trial. Do the data contradict the third law, Luz?
- Yes: cart B read higher in two trials, so B pushed harder
- No: the gaps are 0.3 N or less, within the sensors' 0.5 N accuracy
- Yes: the readings differ, so the forces were not equal
- No: the third law requires the readings to match to the last digit
Block A rides on block B without slipping, and both accelerate at 3 m/s² on a smooth table. Noah says block A pushes nothing on block B, since A just rides along. Using the diagrams, agree or disagree?
- Disagree: A needs 6 N from B, so A pushes back on B with 6 N
- Agree: the hand's 18 N is the one force that acts on block B
- Agree: a block that rides along without slipping exerts no force on the other
- Disagree: A pushes B with 2 N, its mass times 1 m/s²
A 10 N push drives a 2 kg block into a 3 kg block; only the 3 kg block feels 4 N of friction. How hard do the blocks push each other, Ren?
- 2.4 N, the net force on the 2 kg block alone
- 6 N, from 10 N shared by mass, ignoring the friction
- 3.6 N, the 3 kg block's mass times its acceleration
- 7.6 N, since the 3 kg block needs 3 × 1.2 N plus 4 N
Team A is on ice and slips at a rope tension of 150 N. Team B is on rough pavement, and its feet hold. Which way does the contest go, Tala?
- Team A wins, since the ice lets its team pull the rope more easily
- Neither team moves, since the rope forces on them are equal and opposite
- Team A slides toward team B, since only B's feet can hold 150 N
- Team B slides toward team A, since B pulls with the larger force
A 50 kg skater on smooth ice throws a 2 kg ball forward at 5 m/s. How fast does the skater move backward, Zee?
- 5 m/s, since the skater and ball feel equal and opposite forces
- 0.1 m/s, since the skater's mass is spread over 100 kg of load
- 0.04 m/s, since the mass ratio must be squared
- 0.2 m/s, since the skater gets the same momentum as the ball