Deck 5: Newtons Laws of Motion

Question 1

A 47.0-kg person steps on a scale in an elevator. The scale reads 461 N. What is the elevator doing?

Answer 1

It is either at rest or traveling with a constant velocity.

Question 2

The mass of an object is fixed, but its weight varies from location to location.

Answer 2

True

Question 3

A constant net force acts on an object. Describe the motion of the object.

A) constant non-zero velocity.
B) constant non-zero acceleration.
C) increasing acceleration.
D) decreasing acceleration.
E) zero acceleration.

Answer 3

constant non-zero acceleration.

Question 4

An object is moving with constant velocity. Which of the following statements is true?

A) A constant force is being applied in the direction of motion.
B) A constant force is being applied in the direction opposite of motion.
C) There are no forces acting on the object.
D) The net force on the object is zero.
E) There is no frictional force acting on the object.

Question 5

State Newton's second law of motion.

Question 6

State Newton's first law of motion.

Question 7

When a parachutist jumps from an airplane, he eventually reaches a constant speed, called the terminal velocity. This means that

A) the acceleration is equal to g.
B) the force of air resistance is equal to zero.
C) the effect of gravity has died down.
D) the effect of gravity increases as he becomes closer to the ground.
E) the force of air resistance is equal to the weight of the parachutist.

Question 8

When a hunter fires a rifle, the hunter feels a force against her shoulder. Explain why.

Question 9

Mass is a measure of how difficult it is to change the velocity of an object.

Question 10

In the absence of an external force, a moving object will

A) stop immediately.
B) slow down and eventually come to a stop.
C) move faster and faster.
D) move with constant velocity for a while and then slow to a stop.
E) move with constant velocity.

Question 11

When you catch a ball, you feel a force against your hand. Why?

Question 12

An astronaut in a space capsule is experiencing "weightlessness." Does the astronaut have to exert any effort to throw a bowling ball, since the bowling ball is also weightless?

Question 13

A force is required for an object to move.

Question 14

State Newton's third law of motion.

Question 15

Why does it hurt more to fall from a certain height to the ground than it does to fall from the same height into a swimming pool?

Question 16

Force is a vector quantity.

Question 17

The force you exert on Earth is insignificant compared to the force Earth exerts on you.

Question 18

The acceleration of an object does not have to be in the same direction as the net force applied to it.

Question 19

A student uses a plumb bob to verify that the doorjamb in a car is vertical. As the car pulls away from a stop, the student observes that the string now makes an angle θ with the doorjamb. Why does this happen?

Question 20

The mass of the Moon is about 1/80th of the mass of Earth. The force exerted by Earth on the Moon is about 80 times that exerted by the Moon on Earth.

Question 21

FIGURE 5-1
In Figure 5-1, masses m₁ and m₂ are such that m₁ > m₂ and they lay on a level, frictionless surface. We can apply a horizontal force either from the left or from the right. The contact force between masses m₁ and m₂ is

A) zero newtons.
B) larger when is applied from the left.
C) larger when is applied from the right.
D) the same in either case.
E) impossible to determine based on this data.

Question 22

A locomotive is pulling a number of identical wagons along a level track and accelerating. Friction is negligible. Starting from the last wagon, the ratio of the forces between adjacent wagons is

A) 1:2:3:4 . . .
B) 1:2:4:8 . . .
C) 1:3:5:7 . . .
D) . . .
E) 1:1:1:1 . . .

Question 23

A horse pulls a cart with force . As a result of this force the cart accelerates with constant acceleration. What is the magnitude of the force that the cart exerts on the horse?

A) zero Newtons
B) equal to the magnitude of
C) less than the magnitude of
D) more than the magnitude of
E) cannot be determined without additional information

Question 24

You ride on an elevator that is moving downward with constant speed while standing on a bathroom scale. The reading on the scale is

A) equal to your true weight, mg.
B) more than your true weight, mg.
C) less than your true weight, mg.
D) could be more or less than your true weight, mg, depending on the value of the speed.

Question 25

Imagine that the metal head of a hammer is loose. In order to get the hammerhead tight again you should

A) drop the hammer on its side from some given height.
B) drop the hammer with the handle end down.
C) drop the hammer with the head end down.
D) It makes no difference how you drop the hammer, the head will be tightened.
E) It makes no difference how you drop the hammer, the head will not be tightened.

Question 26

A block of mass M slides down a frictionless plane inclined at an angle θ with the horizontal. The normal reaction force exerted by the plane on the block is

A) Mg.
B) Mg sin θ.
C) Mg cos θ.
D) Mg tan θ.
E) zero, since the plane is frictionless.

Question 27

A person is lowering a bucket into a well with a constant speed. The force exerted by the rope on the bucket is

A) equal to the bucket's weight.
B) greater than the bucket's weight.
C) less than the bucket's weight, but not zero N.
D) zero N.
E) Cannot be determined without additional information.

Question 28

What does the word "normal" mean in the phrase "normal force"?

A) the force that is usually exerted by a surface
B) the total force exerted by a surface
C) the component of the force exerted by a surface parallel to the surface
D) the component of the force exerted by a surface perpendicular to the surface
E) the force is due to contact between two objects.

Question 29

A golf club hits a golf ball with a force of 2400 N. The golf ball hits the club with a force

A) slightly less than 2400 N.
B) exactly 2400 N.
C) slightly more than 2400 N.
D) close to 0 N.
E) Cannot be determined without additional information.

Question 30

A block of mass M slides down a frictionless plane inclined at an angle θ with the horizontal. The normal reaction force exerted by the plane on the block is directed

A) parallel to the plane in the same direction as the movement of the block.
B) parallel to the plane in the opposite direction as the movement of the block
C) perpendicular to the plane.
D) toward the center of the Earth.
E) toward the center of mass of the block.

Question 31

An object of weight W is in free-fall close to the surface of Earth. What is the force that the object exerts on Earth?

A) a force greater than W
B) a force less than W
C) a force equal to W
D) no force at all
E) cannot be determined without additional information

Question 32

You ride on an elevator that is moving with constant downward acceleration while standing on a bathroom scale. The reading on the scale is

A) equal to your true weight, mg.
B) less than your true weight, mg.
C) more than your true weight, mg.
D) could be more or less than your true weight, mg, depending on the magnitude of the acceleration.

Question 33

A 20-ton truck collides with a 1500-lb car and causes a lot of damage to the car. Since a lot of damage is done on the car

A) the force on the truck is greater then the force on the car.
B) the force on the truck is equal to the force on the car.
C) the force on the truck is smaller than the force on the car.
D) the truck did not slow down during the collision.
E) the car did not slow down during the collision.

Question 34

A ball is thrown up into the air. Ignore air resistance. When it is rising and reaches half of its maximum height, the net force acting on it is

A) equal to its weight.
B) greater than its weight.
C) less than its weight, but not zero N.
D) zero N.
E) Cannot be determined without additional information.

Question 35

A truck is towing a car whose mass is one quarter that of the truck. The force exerted by the truck on the car is 6000 N. The force exerted by the car on the truck is

A) 1500 N.
B) 24000 N.
C) 3000 N.
D) 6000 N.
E) 12000 N.

Question 36

A student uses a plumb bob to verify that the doorjamb in a car is vertical. As the car pulls away from a stop, the student observes that the string now makes an angle θ with the doorjamb. What is the acceleration of the car?

A) g sin θ
B) g cos θ
C) g tan θ
D) g θ
E) θ

Question 37

An object of mass m sits on a flat table. The Earth pulls on this object with force mg, which we will call the action force. What is the reaction force?

A) The table pushing up on the object with force mg.
B) The object pushing down on the table with force mg.
C) The table pushing down on the floor with force mg.
D) The object pulling upward on the Earth with force mg.
E) The table pulling upward on the Earth with force mg.

Question 38

You apply the same force to two objects. Object 1 has mass M and object 2 has mass 5M. The acceleration of object 2 is

A) ten times that of object 1.
B) five times that of object 1.
C) the same as that of object 1.
D) one-fifth as that of object 1.
E) has no relation to that of object 1.

Question 39

A fireman is sliding down a fire pole. As he speeds up, he tightens his grip on the pole, thus increasing the vertical frictional force that the pole exerts on the fireman. When this force equals the weight of the fireman, what happens?

A) The fireman comes to a stop.
B) The fireman descends with slower and slower speed.
C) The fireman descends with a smaller acceleration.
D) The fireman continues to descend, but with constant speed.
E) Cannot be determined without additional information.

Question 40

A block of mass M slides down a frictionless plane inclined at an angle θ with the horizontal. The gravitational force is directed

A) parallel to the plane in the same direction as the movement of the block.
B) parallel to the plane in the opposite direction as the movement of the block
C) perpendicular to the plane.
D) toward the center of the Earth.
E) toward the center of mass of the block.

Question 41

A flatbed truck is carrying a load of timber which is not tied down. The mass of the timber is 800 kg. The maximum frictional force between the truck bed and the load is 2400 N. What is the highest acceleration that the truck can have without losing its load?

Question 42

Two objects have masses m and 5m, respectively. They both are placed side by side on a frictionless inclined plane and allowed to slide down from rest.

A) It takes the lighter object 5 times longer to reach the bottom of the incline than the heavier.
B) It takes the lighter object 10 times longer to reach the bottom of the incline than the heavier.
C) It takes the heavier object 5 times longer to reach the bottom of the incline than the lighter.
D) It takes the heavier object 10 times longer to reach the bottom of the incline than the lighter.
E) The two objects reach the bottom of the incline at the same time.

Question 43

A 120-kg mass rests on a horizontal surface. What is the magnitude of the normal force exerted by the surface on the mass?

Question 44

A net force of 125 N is applied to a certain object. As a result, the object accelerates with an acceleration of 24.0 m/s². The mass of the object is

A) 3000 kg.
B) 2880 kg.
C) 144 kg.
D) 0.200 kg.
E) 5.20 kg.

Question 45

A block lies on a horizontal frictionless surface. A horizontal force of 100 N is applied to the block giving rise to an acceleration of 3 m/s².
(a) Determine the mass of the block.
(b) Calculate the distance the block will travel is the force is applied for 10 s.
(c) Calculate the speed of the block after the force has been applied for 10 s.

Question 46

What average net force is required to accelerate a car with a mass of 1200 kg from 0 to 27.0 m/s in 10.0 s?

A) 444 N
B) 1620 N
C) 3240 N
D) 4360 N
E) 11800 N

Question 47

A block lies on a smooth inclined plane tilted at an angle of 35° to the horizontal.
(a) Draw the free-body diagram for the block.
(b) Determine the block's acceleration as it slides down the inclined plane.
(c) If the block started from rest 8.5 m up the incline from its base, determine the block's speed when it reaches the bottom of the incline.
(d) How long did it take the block to reach the bottom of the inclined plane?

Question 48

A student pulls a box of books on a smooth horizontal floor with a force of 100 N in a direction of 37.0° above the horizontal. The mass of the box and the books is 40.0 kg.
(a) Draw the free-body diagram for the box.
(b) Calculate the acceleration of the box.
(c) Calculate the normal force acting on the box.

Question 49

A net force of 450 N applied to a car results in the car accelerating at 0.360 m/s². What is the mass of the car?

A) 162 kg
B) 625 kg
C) 12300 kg
D) 1250 kg
E) 1590 kg

Question 50

The mass of a proton is 1.7 × 10^-27 kg. What is the weight of 6.0 × 10²³ protons?

Question 51

To determine the mass of a car, a student (with a friend at the wheel) pushes the car holding a bathroom scale between himself and the car and carefully maintains a constant reading of 400 N on the scale while the car accelerates on level ground. At the conclusion of the experiment his friend reports that the car accelerated from rest to 14.0 km/hr in 12.0 s. What was the mass of the car?

A) 343 kg
B) 1230 kg
C) 2460 kg
D) 3360 kg
E) 3430 kg

Question 52

A catcher stops a ball traveling at 40 m/s in a distance of 20 cm and feels a force of 600 N against his glove. What is the mass of the ball?

A) 0.10 kg
B) 0.15 kg
C) 0.20 kg
D) 0.25 kg
E) 0.30 kg

Question 53

A 777 aircraft has a mass of 300,000 kg. At a certain instant during its landing, its speed is 27.0 m/s. If the braking force is 435,000 N, how much further does it travel along the runway before it comes to a stop?

A) 40.5 m
B) 142 m
C) 181 m
D) 251 m
E) 456 m

Question 54

In a particle accelerator, a proton reaches an acceleration of 9.0 × 10¹³ m/s². The mass of a proton is 1.7 × 10^-27 kg. What is the force on the proton?

Question 55

On a hard stop, the deceleration of a car is 8.00 m/s². What force does a 50.0-kg passenger exert on the seat belt in such a stop?

Question 56

A 45-kg person steps on a scale in an elevator. The scale reads 460 N. What is the elevator doing?

Question 57

A 777 aircraft has a mass of 300,000 kg. At a certain instant during its landing, its speed is 27.0 m/s. If the braking force is 445,000 N, what is the speed of the airplane 10.0 s later?

A) 10.0 m/s
B) 12.2 m/s
C) 14.0 m/s
D) 18.0 m/s
E) 20.0 m/s

Question 58

A force of 120 N is applied to an object whose mass is 30 kg. The object's acceleration is

A) 3600 m/s².
B) 150 m/s².
C) 4.0 m/s²
D) 2.0 m/s².
E) 0.25 m/s².

Question 59

An object rests on an inclined surface. If the inclination of the surface is made steeper, what does the normal force on the object do?

A) increase
B) decrease
C) stays the same
D) The normal force is zero N.
E) Cannot be determined without additional information.

Question 60

The locking mechanism for the seatbelt of a car makes use of the fact that the apparent vertical direction (i.e. the direction in which a plumb bob hangs) changes with the car's deceleration. In a certain collision, the deceleration of a car is 5.00 g. What angle does the apparent vertical make with the true vertical?

Question 61

A 1200-kg car is pulling a 500-kg trailer along level ground. Friction is negligible. The car accelerates with an acceleration of 1.3 m/s². What is the force exerted by the car on the trailer?

A) 550 N
B) 600 N
C) 650 N
D) 700 N
E) 750 N

Question 62

Three boxes rest side-by-side on a smooth, horizontal floor. Their masses are 5.0 kg, 3.0 kg, and 2.0 kg, with the 3.0-kg mass in the center. A force of 50 N pushes on the 5.0-kg mass, which pushes against the other two masses. What is the contact force between the 3.0-kg mass and the 2.0-kg mass?

A) 0 N
B) 10 N
C) 25 N
D) 40 N
E) 50 N

Question 63

A 3.0-kg and a 5.0-kg box rest side-by-side on a smooth, level floor. A horizontal force of 32 N is applied to the 5.0-kg box pushing it against the 3.0-kg box, and, as a result, both boxes slide along the floor. How large is the contact force between the two boxes?

A) 12 N
B) 20 N
C) 24 N
D) 32 N
E) 0 N

Question 64

A 50.0-kg crate is being pulled along a horizontal, smooth surface. The pulling force is 10.0 N and is directed 20.0° above the horizontal. What is the acceleration of the crate?

A) 0.0684 m/s²
B) 0.188 m/s²
C) 0.200 m/s²
D) 0.376 m/s²
E) 0.0728 m/s²

Question 65

A load is being lifted by means of two cables attached to it. The first cable exerts a force of 600 N at an angle of 35° to the left of the vertical. The second cable exerts a force of 1300 N. If the load is accelerating vertically, at what angle to the right of the vertical is the second cable pulling?

A) 15.4°
B) 16.2°
C) 30.8°
D) 67.8°
E) 75.8°

Question 66

A 3.0-kg and a 5.0-kg box rest side-by-side on a smooth, level floor. A horizontal force of 32 N is applied to the 3.0-kg box pushing it against the 5.0-kg box, and, as a result, both boxes slide along the floor. How large is the contact force between the two boxes?

A) 12 N
B) 20 N
C) 24 N
D) 32 N
E) 0 N

Question 67

Three boxes rest side-by-side on a smooth, horizontal floor. Their masses are 5.0 kg, 3.0 kg, and 2.0 kg, with the 3.0-kg mass in the center. A force of 50 N pushes on the 2.0-kg mass, which pushes against the other two masses. What is the contact force between the 3.0-kg mass and the 2.0-kg mass?

A) 0 N
B) 10 N
C) 25 N
D) 40 N
E) 50 N

Question 68

FIGURE 5-3
The three forces represented in Figure 5-3 act on an object. What is the direction of the acceleration of the object?

A) 11.3° clockwise from the -x-axis
B) 11.3° counterclockwise from the +y-axis
C) 78.7° counterclockwise from the +x-axis
D) 11.3° clockwise from the +y-axis
E) The mass of the object must be known to answer the question.

Question 69

Three boxes rest side-by-side on a smooth, horizontal floor. Their masses are 5.0 kg, 3.0 kg, and 2.0 kg, with the 3.0-kg mass in the center. A force of 50 N pushes on the 2.0-kg mass, which pushes against the other two masses. What is the contact force between the 5.0-kg mass and the 3.0-kg mass?

A) 0 N
B) 10 N
C) 25 N
D) 40 N
E) 50 N

Question 70

A locomotive is pulling three wagons along a level track with a force of 100,000 N. The wagon next to the locomotive has a mass of 70,000 kg, the next one, 50,000 kg, and the last one, 80,000 kg. Neglect friction. What is the force between the 80,000-kg and 50,000-kg wagons?

A) 35,000 N
B) 40,000 N
C) 50,000 N
D) 60,000 N
E) 65,000 N

Question 71

Three boxes rest side-by-side on a smooth, horizontal floor. Their masses are 5.0 kg, 3.0 kg, and 2.0 kg, with the 3.0-kg mass in the center. A force of 50 N pushes on the 5.0-kg mass, which pushes against the other two masses. What is the contact force between the 5.0-kg mass and the 3.0-kg mass?

A) 0 N
B) 10 N
C) 25 N
D) 40 N
E) 50 N

Question 72

A locomotive is pulling three wagons along a level track with a force of 100,000 N. The wagon next to the locomotive has a mass of 70,000 kg, the next one, 50,000 kg, and the last one, 80,000 kg. Neglect friction. What is the force between the 70,000-kg and 50,000-kg wagons?

A) 35,000 N
B) 40,000 N
C) 50,000 N
D) 60,000 N
E) 65,000 N

Question 73

FIGURE 5-2
The two forces indicated in Figure 5-2 act on a 3.00-kg object. What is the acceleration of the object?

A) (1.67 m/s²) - (0.333 m/s²)
B) (5.00 m/s²) + (1.00 m/s²)
C) (1.67 m/s²) + (2.333 m/s²)
D) (15.0 m/s²) + (3.00 m/s²)
E) (1.67 m/s²) + (0.333 m/s²)

Question 74

Two forces act on a 4.00-kg object in a manner that the object has an acceleration 3.00 m/s² in a direction 20.0° north of east. The first force is 15.00 N in a direction 10.0° west of north. What is the second force?

A) 14.6 N in a direction 28.1° south of east
B) 12.9 N in a direction 28.1° south of east
C) 16.2 N in a direction 30.2° south of east
D) 18.8 N in a direction 41.1° south of east
E) 17.5 N in a direction 37.5° south of east

Question 75

A 40.0-kg box is being pushed along a horizontal, smooth surface. The pushing force is 15.0 N directed at an angle of 15.0° below the horizontal. What is the acceleration of the crate?

A) 0.158 m/s²
B) 0.362 m/s²
C) 0.466 m/s²
D) 0.375 m/s²
E) 0.684 m/s²

Question 76

A locomotive is pulling three wagons along a level track with a force of 100,000 N. The wagon next to the locomotive has a mass of 80,000 kg, the next one, 50,000 kg, and the last one, 70,000 kg. Neglect friction. What is the force between the 80,000-kg and 50,000-kg wagons?

A) 35,000 N
B) 40,000 N
C) 50,000 N
D) 60,000 N
E) 65,000 N

Question 77

FIGURE 5-4
The free-body diagram of an 8.00 kg object is shown in Figure 5-4. What is Newton's Second Law for this object?

A) (6.0 N sin 28° - 5.0 N sin 22°) + (6.0 N cos 28° + 5.0 N cos 22°) = (8.00 kg)
B) (6.0 N cos 28° + 5.0 N cos 22°) + (6.0 N sin 28° + 5.0 N sin 22°) = (8.00 kg)
C) (6.0 N cos 28° - 5.0 N sin 22°) + (6.0 N sin 28° + 5.0 N cos 22°) = (8.00 kg)
D) (6.0 N cos 28° - 5.0 N cos 22°) + (6.0 N sin 28° + 5.0 N sin 22°) = (8.00 kg)
E) (6.0 N cos 28° + 5.0 N sin 22°) ⁱ + (6.0 N sin 28° - 5.0 N cos 22°) = (8.00 kg)

Question 78

The following four forces act on a 4.00 kg object:
F₁ = 300 N east
F₂ = 700 N north
F₃ = 500 N west
F₄ = 600 N south
What is the acceleration of the object?

A) 224 N in a direction 63.4° north of west
B) 300 N in a direction 63.4° north of west
C) 300 N in a direction 26.6° north of west
D) 224 N in a direction 26.6° north of west
E) 2100 N in a direction 26.6° north of west

Question 79

A locomotive is pulling three wagons along a level track with a force of 100,000 N. The wagon next to the locomotive has a mass of 80,000 kg, the next one, 50,000 kg, and the last one, 70,000 kg. Neglect friction. What is the force between the 50,000-kg and 70,000-kg wagons?

A) 35,000 N
B) 40,000 N
C) 50,000 N
D) 60,000 N
E) 65,000 N

Question 80

A 1000-kg barge is being towed by means of two horizontal cables. One cable is pulling with a force of 80.0 N in a direction 30.0° west of north. In what direction should the second cable pull so that the barge will accelerate northward, if the force exerted by the cable is 120 N?

A) 19.5° east of north
B) 21.1° east of north
C) 39.0° east of north
D) 47.5° east of north
E) 54.7° east of north