Q: A Boeing 737 (mass $$51,000 \ \mathrm{kg}) $$accelerates from rest to $$70 \ \mathrm{m/s}$$ over a distance of $$940 \ \mathrm{m} on a $$runway. What is the magnitude of the net force required to produce this acceleration? (Ignore friction and air resistance.)

$$1.3 \times 10^5$ \ \mathrm{N}$$

Q: A 5 kg object is acted on by two forces: $$F_1 = 10$$ \ \mathrm{N}$$ to the right and F_2$ = 4 \ \mathrm{N} to $$the left. What is the acceleration of the object?

$$2 \ \mathrm{m/s^2$}$$ \text{ to the right}

Question 1

A 70 kg astronaut in deep space (far from any planets or stars) pushes on a 200 kg satellite. According to Newton’s third law, what is true about the forces involved?

Accepted Answer

The force the astronaut exerts on the satellite is equal in magnitude and opposite in direction to the force the satellite exerts on the astronaut.

Question 2

A car is moving at a constant velocity on a straight, level road. Which of the following statements is correct about the net force acting on the car?

Accepted Answer

The net force is zero.

Question 3

A 2 kg block is pulled across a horizontal surface by a constant force of 10 N. If the block accelerates at $$3 \ \mathrm{m/s^2$}$$, what is the magnitude of the frictional force acting on the block?

Accepted Answer

$$6 \ \mathrm{N}$$

Question 4

A skydiver reaches terminal velocity during a fall. Which of the following is true about the forces acting on the skydiver?

Accepted Answer

The net force is zero.

Question 5

A 1000 kg car is at rest on a flat road. What is the magnitude of the normal force exerted by the road on the car?

Accepted Answer

$$9800 \ \mathrm{N}$$

Question 6

A block is pulled with a constant force $$F$$ and moves with a constant acceleration $$a. If $$the mass of the block is doubled and the same force is applied, what will be the new acceleration?

Accepted Answer

$$a/2$$

Question 7

A ball is thrown straight up. Ignore air resistance. What is the correct free-body diagram for the ball just after it leaves the thrower’s hand?

Accepted Answer

A single downward force representing gravity.

Question 8

A 60 kg skier is being towed up a frictionless hill at a constant speed by a rope. What is the net force acting on the skier?

Accepted Answer

$$0 \ \mathrm{N}$$

Question 9

A Boeing 737 (mass $$51,000 \ \mathrm{kg}) $$accelerates from rest to $$70 \ \mathrm{m/s}$$ over a distance of $$940 \ \mathrm{m} on a $$runway. What is the magnitude of the net force required to produce this acceleration? (Ignore friction and air resistance.)

Accepted Answer

$$1.3 	imes 10^5$ \ \mathrm{N}$$

Question 10

A person stands motionless on a bathroom scale in an elevator that is moving upward and slowing down. How does the reading on the scale compare to the person’s true weight?

Accepted Answer

The scale reads more than the true weight.

Question 11

A block is at rest on an inclined plane. Which force prevents the block from sliding down the plane?

Accepted Answer

Static friction

Question 12

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

Accepted Answer

Both exert equal and opposite forces on each other.

Question 13

A 5 kg object is acted on by two forces: $$F_1 = 10$$ \ \mathrm{N}$$ to the right and F_2$ = 4 \ \mathrm{N} to $$the left. What is the acceleration of the object?

Accepted Answer

$$2 \ \mathrm{m/s^2$}$$ 	ext{ to the right}

Question 14

A block is pulled across a rough surface at a constant speed. Which of the following statements is correct?

Accepted Answer

The pulling force is equal to the friction force.

Question 15

A 10 kg box is suspended by a rope. If the box is lowered at a steadily decreasing speed, what can you say about the tension in the rope?

Accepted Answer

The tension is greater than the weight of the box.

Question 16

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

Accepted Answer

Orthogonal force

Question 17

A runner pushes backward on the ground with her foot and accelerates forward. Which force is responsible for her forward acceleration?

Accepted Answer

The static friction force

Question 18

A ball rolls off a horizontal table. Ignoring air resistance, what forces act on the ball as it moves through the air?

Accepted Answer

A downward force due to gravity only

Question 19

A 1 kg block is pulled with a constant force and accelerates at $$2 \ \mathrm{m/s^2$}. If a $$second block is pulled with the same force and accelerates at $$4 \ \mathrm{m/s^2$}$$, what is the mass of the second block?

Accepted Answer

$$0.5 \ \mathrm{kg}$$

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

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