Question 1

A car crashes into a wall and comes to a sudden stop, but the crash test dummy inside continues moving forward until it hits the dashboard. Which law of motion best explains why the dummy keeps moving?

Accepted Answer

Newton's first law: An object in motion remains in motion unless acted on by a net force.

Question 2

A 60.0-kg passenger in a car experiences a horizontal force of $$4.00 	imes 10^2$\ \mathrm{N}$$ during a crash. What is the passenger's acceleration?

Accepted Answer

$$a = 6.67\ \mathrm{m/s^2$}$$

Question 3

Which of the following is a long-range force?

Accepted Answer

Weight (gravitational force)

Question 4

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

Accepted Answer

The weight of the ball acting vertically down.

Question 5

A steel beam hangs from a cable as a crane lifts the beam. What forces act on the beam?

Accepted Answer

Gravity and tension in the cable

Question 6

A 100-kg block hangs on a rope. What is the tension in the rope if the block is stationary?

Accepted Answer

$$T = 980\ \mathrm{N}$$

Question 7

A car with a mass of $$1500\ \mathrm{kg} is $$being towed at a steady speed by a rope held at a $$20^\circ$$ angle from the horizontal. A friction force of $$320\ \mathrm{N}$$ opposes the car’s motion. What is the tension in the rope?

Accepted Answer

$$T = 340\ \mathrm{N} / \cos 20^\circ$$

Question 8

A sled with a mass of $$20\ \mathrm{kg}$$ slides along frictionless ice at $$4.5\ \mathrm{m/s}. It $$then crosses a rough patch of snow that exerts a friction force of $$12\ \mathrm{N}. $$How far does it slide on the snow before coming to rest?

Accepted Answer

$$d = 16.9\ \mathrm{m}$$

Question 9

Which of the following statements about Newton’s third law is correct?

Accepted Answer

Action and reaction forces are always equal in magnitude and opposite in direction.

Question 10

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

Accepted Answer

Only the force of gravity acting downward.

Question 11

A block is at rest on a horizontal surface. Which of the following statements is true about the forces acting on the block?

Accepted Answer

The normal force is equal in magnitude and opposite in direction to the weight.

Question 12

A rocket expels exhaust gases downward. According to Newton’s third law, what is the reaction force?

Accepted Answer

The exhaust gases push the rocket upward.

Question 13

A skier is pulled up a hill at constant speed by a rope. Which statement is true about the net force acting on the skier?

Accepted Answer

The net force is zero.

Question 14

A ball weighing $$50\ \mathrm{N} is $$pulled back by a rope at an angle of $$20^\circ$$ from the vertical. What is the tension in the rope?

Accepted Answer

$$T = 50\ \mathrm{N}$$

Question 15

A car is towed to the right at constant speed. Which of the following statements is correct about the forces acting on the car?

Accepted Answer

The net force is zero.

Question 16

A ball hangs from the ceiling by a string and is pulled back and released. Just after its release, which forces act on the ball?

Accepted Answer

Tension and gravity

Question 17

An object on a rope is lowered at a steadily decreasing speed. Which is true?

Accepted Answer

The rope tension is greater than the object’s weight.

Question 18

A constant force causes an object to accelerate at $$a. $$What is the acceleration of an object with twice the mass that experiences the same force?

Accepted Answer

$$a/2$$

Question 19

A 40-car train travels along a straight track at $$40\ \mathrm{mph}. A $$skier speeds up as she skis downhill. On which is the net force greater?

Accepted Answer

The skier

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

Study Guide - Practice Questions

Study Guide - Flashcards