Question 1

A 10-kg box is pushed across a rough floor with a constant velocity. If the force of friction is 40 N, what is the magnitude of the applied force?

Accepted Answer

$$40\ \mathrm{N}$$

Question 2

Which of the following best describes the relationship between mass and weight?

Accepted Answer

Weight is the force of gravity on an object and is proportional to its mass.

Question 3

A skydiver jumps from a plane and accelerates downward. As her speed increases, what happens to the air resistance acting on her?

Accepted Answer

It increases.

Question 4

If a net force of $$30\ \mathrm{N}$$ acts on a $$5\ \mathrm{kg}$$ object, what is its acceleration?

Accepted Answer

$$6\ \mathrm{m/s^2$}$$

Question 5

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 $$10\ \mathrm{m/s}$$, what is the speed of the 10-kg ball?

Accepted Answer

$$10\ \mathrm{m/s}$$

Question 6

A 60-kg astronaut is floating in space far from any planets. What is her weight?

Accepted Answer

$$0\ \mathrm{N}$$

Question 7

A car of mass $$m$$ accelerates at $$a$$ when a net force $$F is $$applied. If the mass is doubled and the same force is applied, what is the new acceleration?

Accepted Answer

$$\frac{a}{2}$$

Question 8

A 20-N object falls through air and experiences 5 N of air resistance. What is the object's acceleration? (Take $$g = 10\ \mathrm{m/s^2$})$$

Accepted Answer

$$7.5\ \mathrm{m/s^2$}$$

Question 9

Which of the following statements about terminal velocity is correct?

Accepted Answer

It occurs when the net force on the object is zero.

Question 10

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

Accepted Answer

The heavy person, because they have a greater terminal speed.

Question 11

If the net force on a cart is doubled and its acceleration remains unchanged, what must have happened to the cart's mass?

Accepted Answer

It doubled.

Question 12

A rock and a feather are dropped in a vacuum. Which statement is true?

Accepted Answer

Both hit the ground at the same time.

Question 13

A refrigerator is pushed across a kitchen floor at a constant speed. What can you say about the force of friction compared to the applied force?

Accepted Answer

Friction is equal and opposite to the applied force.

Question 14

If the mass of an object is halved, what happens to its weight on Earth?

Accepted Answer

It is halved.

Question 15

A 1-kg object weighs how much on Earth's surface? (Use $$g = 9.8\ \mathrm{m/s^2$})$$

Accepted Answer

$$9.8\ \mathrm{N}$$

Question 16

When a skydiver reaches terminal velocity, what is the relationship between the force of gravity and the force of air resistance?

Accepted Answer

Gravity and air resistance are equal in magnitude.

Question 17

A 5-kg object is in free fall. What is the net force acting on it? (Use $$g = 10\ \mathrm{m/s^2$})$$

Accepted Answer

$$50\ \mathrm{N}$$

Question 18

If you pull down quickly on the bottom string of a ball hanging from two strings, which string breaks and what does this demonstrate?

Accepted Answer

The bottom string breaks, demonstrating mass (inertia).

Question 19

Which of the following is NOT a factor that affects the force of friction between two surfaces?

Accepted Answer

The speed at which the surfaces move.

Newton's Second Law of Motion: Force, Mass, and Acceleration

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