Q: A 2.0 kg block is pulled with a constant force, resulting in an acceleration of $$3.0\ \mathrm{m/s^2$}. $$What is the magnitude of the net force applied?

$$F = 2.0 \times 3.0 = 6.0\ \mathrm{N}$$

Question 1

A 1500 kg car is pushed by two people. One person applies a force of 300 N east, and the other applies 400 N east. If friction opposes the motion with a force of 250 N, what is the acceleration of the car?

Accepted Answer

$$a = \frac{300 + 400 - 250}{1500} = 0.3\ \mathrm{m/s^2$}$$

Question 2

A skydiver has reached terminal velocity. Which statement is correct about the forces acting on her?

Accepted Answer

There is no net force.

Question 3

A ball is rolling down an incline and leaves a horizontal ramp. Ignoring air resistance, what force(s) act on the ball just after it leaves the ramp?

Accepted Answer

The weight of the ball acting vertically down.

Question 4

Which of the following is NOT a force discussed in this chapter?

Accepted Answer

The orthogonal force

Question 5

A 2.0 kg block is pulled with a constant force, resulting in an acceleration of $$3.0\ \mathrm{m/s^2$}. $$What is the magnitude of the net force applied?

Accepted Answer

$$F = 2.0 	imes 3.0 = 6.0\ \mathrm{N}$$

Question 6

A skier is being towed up a hill at constant speed. Which statement about the forces acting on the skier is correct?

Accepted Answer

The net force is zero.

Question 7

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

Accepted Answer

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

Question 8

A 1.0 kg block is pulled with a constant force and accelerates at $$2.0\ \mathrm{m/s^2$}. If a $$second block with unknown mass is pulled with the same force and accelerates at $$4.0\ \mathrm{m/s^2$}$$, what is the mass of the second block?

Accepted Answer

$$0.5\ \mathrm{kg}$$

Question 9

Which of the following best describes Newton’s third law?

Accepted Answer

Every force occurs as one member of an action/reaction pair, acting on two different objects in opposite directions.

Question 10

A box is at rest on a horizontal surface. Which forces act on the box?

Accepted Answer

Weight force and normal force

Question 11

A 40-car train travels at constant speed on a straight track, while a skier speeds up as she skis downhill. On which is the net force greater?

Accepted Answer

The skier

Question 12

A ball is tossed straight up. Just after it leaves the hand (ignore air resistance), which force(s) act on it?

Accepted Answer

Only the weight force, acting downward.

Question 13

A block is pulled to the right with a constant, steady force. How will its acceleration graph look?

Accepted Answer

A horizontal line above the time axis (constant acceleration)

Question 14

A man paddles a raft (total mass 1300 kg) with a force of 17 N due east. The wind exerts a force of 15 N at $$67^\circ$$ north of east. What is the x-component of the raft’s acceleration?

Accepted Answer

$$a_x = \frac{17 + 15 \cos 67^\circ}{1300}\ \mathrm{m/s^2$}$$

Question 15

A bobsledder pushes her sled across horizontal snow to get it going, then jumps in. After she jumps in, the sled gradually slows to a halt. What forces act on the sled just after she’s jumped in?

Accepted Answer

Gravity, a normal force, and kinetic friction

Question 16

A person stands on a hard stone floor. What happens to the floor under their weight?

Accepted Answer

The floor deforms very slightly under their weight.

Question 17

A rope lowers an object at constant speed. Which is true?

Accepted Answer

The rope tension equals the object’s weight.

Question 18

Which of the following is a correct statement about friction?

Accepted Answer

Kinetic friction acts as an object slides across a surface and always opposes the motion.

Question 19

A 5 kg object is acted on by a net force of 20 N. What is its acceleration?

Accepted Answer

$$a = \frac{20}{5} = 4\ \mathrm{m/s^2$}$$

Chapter 4: Forces and Newton’s Laws of Motion – Structured Study Notes

Study Guide - Practice Questions

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