Question 1

Which of the following best describes Newton's First Law of Motion?

Accepted Answer

An object will remain at rest or move in a straight line at constant speed unless acted upon by a net external force.

Question 2

A 2 kg object is acted on by a net force of 10 N. What is its acceleration?

Accepted Answer

$$a = \frac{F}{m} = \frac{10}{2} = 5\ \mathrm{m/s^2$}$$

Question 3

Which of the following statements about Newton's Third Law is correct?

Accepted Answer

For every force, there is an equal and opposite force acting on a different object.

Question 4

A hammer strikes a nail. According to Newton's Third Law, which force pair is correct?

Accepted Answer

The hammer exerts a force on the nail, and the nail exerts an equal and opposite force on the hammer.

Question 5

A mosquito collides head-on with a truck. Which statement is true during the collision?

Accepted Answer

The mosquito exerts the same magnitude force on the truck as the truck exerts on the mosquito.

Question 6

If the net force on an object is zero, what can be said about its motion?

Accepted Answer

It will remain at rest or move at constant velocity in a straight line.

Question 7

A person is walking forward by pushing backward on the ground. What force actually moves the person forward?

Accepted Answer

The static friction force of the ground on the person.

Question 8

A rocket moves forward by expelling hot gases backward. According to Newton's Third Law, what is the action-reaction pair?

Accepted Answer

The rocket exerts a force on the gases backward, and the gases exert an equal and opposite force on the rocket forward.

Question 9

Which of the following is NOT a correct statement about forces?

Accepted Answer

A force always acts on two objects at once in the same direction.

Question 10

Two objects, A and B, are pushed with the same force. If object A has twice the mass of object B, what is the ratio of their accelerations ($$a_A to$$ $$a_B$$)?

Accepted Answer

$$a_A : a_B = 0.5 : 1$$

Question 11

Which of the following best describes an action/reaction pair according to Newton's Third Law?

Accepted Answer

Two forces that are equal in magnitude, opposite in direction, and act on different objects.

Question 12

A 5-year-old stands on a skateboard and is pushed by her brother. If the brother exerts a force of 30 N on her, what is the magnitude of the force she exerts on him?

Accepted Answer

30 N

Question 13

Which of the following is the correct SI unit for force, and what does it represent?

Accepted Answer

Newton (N), which is the force required to accelerate 1 kg at 1 m/s$$^2$$

Question 14

A car tire pushes backward on the road. What is the reaction force according to Newton's Third Law?

Accepted Answer

The road pushes forward on the tire with equal magnitude.

Question 15

Which of the following is a correct free-body diagram principle?

Accepted Answer

All forces acting ON the object are represented as vectors originating from the object.

Question 16

A 10 kg box is at rest on a horizontal surface. The net force acting on the box is zero. What is the acceleration of the box?

Accepted Answer

$$a = 0\ \mathrm{m/s^2$}$$

Question 17

Which of the following is an example of a long-range force?

Accepted Answer

Gravitational force between the Earth and the Moon.

Question 18

If a net force of 50 N acts on a 25 kg object, what is its acceleration?

Accepted Answer

$$a = \frac{F}{m} = \frac{50}{25} = 2\ \mathrm{m/s^2$}$$

Question 19

Which of the following best describes static friction in the context of walking?

Accepted Answer

Static friction prevents your foot from slipping and allows you to push against the ground to move forward.

L10-12: Newton's Laws of Motion: Principles, Applications, and Examples

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