Question 1

Which of Newton's laws explains why a rocket launches upward when its engines expel gas downward?

Accepted Answer

Newton's Third Law: For every action, there is an equal and opposite reaction.

Question 2

A person jumps off a boat onto a dock. What happens to the boat and why?

Accepted Answer

The boat moves away from the dock due to the reaction force from the jump.

Question 3

A car of mass $$m$$ accelerates at rate $$a$$ due to a net force $$F. $$Which equation correctly relates these quantities?

Accepted Answer

$$F = m 	imes a$$

Question 4

If a 2 kg object is pushed with a force of 10 N, what is its acceleration?

Accepted Answer

$$a = 5 	ext{ m/s}^2$$

Question 5

A person stands on a skateboard and throws a ball forward. What happens to the person and why?

Accepted Answer

The person moves backward due to the reaction force from throwing the ball.

Question 6

A 5 kg object is at rest. A force of 15 N is applied for 2 seconds. What is its final velocity?

Accepted Answer

$$v = 3 	ext{ m/s}$$

Question 7

A swimmer pushes off the wall of a pool. What law explains the swimmer's motion away from the wall?

Accepted Answer

Newton's Third Law

Question 8

A 10 kg box is pulled with a force of 40 N. What is its acceleration?

Accepted Answer

$$a = 4 	ext{ m/s}^2$$

Question 9

A person on ice skates throws a heavy object forward. What happens to the person?

Accepted Answer

The person moves backward due to conservation of momentum.

Question 10

A 3 kg object is dropped from rest. Ignoring air resistance, what is its velocity after 2 seconds? (Use $$g = 9.8 	ext{ m/s}^2)$$

Accepted Answer

$$v = 19.6 	ext{ m/s}$$

Question 11

A person pushes a wall but the wall does not move. What force does the wall exert on the person?

Accepted Answer

A force equal in magnitude and opposite in direction to the person's push.

Question 12

A 4 kg object moving at $$2 	ext{ m/s}$$ collides with a stationary 2 kg object. If they stick together, what is their final velocity?

Accepted Answer

$$v = 1.33 	ext{ m/s}$$

Question 13

A person stands on a frictionless surface and throws a ball of mass $$m$$ with velocity $$v. $$What is the recoil velocity of the person if their mass is $$M$$?

Accepted Answer

$$v_{person} = \frac{m}{M} v$$

Question 14

A 6 kg object is acted on by a net force of 18 N. What is its acceleration?

Accepted Answer

$$a = 3 	ext{ m/s}^2$$

Question 15

A person jumps off a raft into the water. What happens to the raft?

Accepted Answer

The raft moves in the opposite direction due to Newton's Third Law.

Question 16

A 2 kg object is moving at $$3 	ext{ m/s}$$ and collides elastically with a 1 kg object at rest. What is the velocity of the 1 kg object after the collision?

Accepted Answer

Question 17

A person pushes a box across the floor. What force opposes the motion?

Accepted Answer

Friction

Question 18

A 5 kg object is dropped from a height. What is the force of gravity acting on it?

Accepted Answer

$$F = 49 	ext{ N}$$

Question 19

A person throws a ball upward. What force acts on the ball after it leaves the person's hand?

Accepted Answer

Only the force of gravity.

Question 20

A 10 kg object is moving at $$5 	ext{ m/s}. $$What is its momentum?

Accepted Answer

$$p = 50 	ext{ kg m/s}$$

Newton's Third Law and Applications in Physics

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