Q: Which equation correctly represents Newton's Second Law of Motion?

$$a = \frac{F_{\text{net}}}{m}$$

Q: A 10-kg object is acted on by a net force of 30 N. What is its acceleration?

$$a = \frac{F_{\text{net}}}{m} = \frac{30}{10} = 3\ \text{m/s}^2$$

Q: A car of mass 1000 kg accelerates at $$2\ \text{m/s}^2. $$What is the net force acting on the car?

$$F_{\text{net}} = m a = 1000 \times 2 = 2000\ \text{N}$$

Question 1

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

Accepted Answer

An object will remain at rest or in uniform motion in a straight line unless acted upon by a nonzero net force.

Question 2

A magician quickly pulls a tablecloth from under a set of dishes, and the dishes remain nearly in place. This is an example of:

Accepted Answer

Inertia

Question 3

Which of the following statements about friction is correct?

Accepted Answer

Friction always acts opposite to the direction of motion or intended motion.

Question 4

A person pushes a refrigerator across a kitchen floor at a constant speed. The force of friction between the refrigerator and the floor is:

Accepted Answer

Equal and opposite to the person's push.

Question 5

If the net force acting on an object is doubled, what happens to its acceleration?

Accepted Answer

The acceleration is doubled.

Question 6

Which equation correctly represents Newton's Second Law of Motion?

Accepted Answer

$$a = \frac{F_{	ext{net}}}{m}$$

Question 7

A cart is pushed along a track with a constant force. If the mass of the cart is halved, what happens to its acceleration?

Accepted Answer

The acceleration doubles.

Question 8

A 5-kg iron ball and a 10-kg iron ball are dropped from rest in a vacuum. When the 5-kg ball reaches a speed of 10 m/s, the speed of the 10-kg ball is:

Accepted Answer

10 m/s

Question 9

When a 20-N falling object encounters 5 N of air resistance, its acceleration is:

Accepted Answer

Less than $$g$$

Question 10

A skydiver jumps from a plane. As the skydiver falls faster and faster through the air, what happens to the air resistance?

Accepted Answer

It increases.

Question 11

When an object falls at terminal velocity, which of the following is true?

Accepted Answer

The force of gravity equals the force of air resistance.

Question 12

If a 50-N person is to fall at terminal speed, the air resistance needed is:

Accepted Answer

50 N

Question 13

A coin and a feather are dropped in a vacuum. What happens?

Accepted Answer

Both the coin and feather drop together side-by-side.

Question 14

Which of the following factors does NOT affect the force of sliding friction between two solid surfaces?

Accepted Answer

The speed of sliding.

Question 15

A heavy and a light person jump together with same-size parachutes from the same altitude. Who will reach the ground first?

Accepted Answer

The heavy person.

Question 16

Which of the following best explains why a coin falls faster than a feather in air, but not in a vacuum?

Accepted Answer

Air resistance affects the feather more than the coin.

Question 17

A 10-kg object is acted on by a net force of 30 N. What is its acceleration?

Accepted Answer

$$a = \frac{F_{	ext{net}}}{m} = \frac{30}{10} = 3\ 	ext{m/s}^2$$

Question 18

Which of the following is true about terminal velocity?

Accepted Answer

It is the constant speed reached when the force of gravity is balanced by air resistance.

Question 19

A car of mass 1000 kg accelerates at $$2\ 	ext{m/s}^2. $$What is the net force acting on the car?

Accepted Answer

$$F_{	ext{net}} = m a = 1000 	imes 2 = 2000\ 	ext{N}$$

Question 20

Which of the following is a correct statement about free fall?

Accepted Answer

All objects accelerate at the same rate regardless of mass, if air resistance is negligible.

Newton’s Second Law of Motion and Related Concepts

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