Deck 4: Dynamics: Newtons Laws of Motion

Question 1

Choose the one alternative that best completes the statement or answers the question.
A satellite is in orbit around the earth. Which one feels the greater force?

A) the earth because the satellite has so little mass
B) It depends on the distance of the satellite from Earth.
C) Earth and the satellite feel exactly the same force.
D) the satellite because the earth is so much more massive

Answer 1

Earth and the satellite feel exactly the same force.

Question 2

Choose the one alternative that best completes the statement or answers the question.
If the rockets of a spaceship in outer space (far from all gravity) suddenly lose power and go off,
the spaceship will gradually slow to a stop.

Answer 2

False

Question 3

Choose the one alternative that best completes the statement or answers the question.
A crate is sliding down an inclined ramp at a constant speed of 0.55 m/s. The vector sum of all the forces acting on this crate must point

A) perpendicular to the ramp.
B) down the ramp.
C) up the ramp.
D) vertically downward.
E) None of the above choices is correct.

Answer 3

None of the above choices is correct.

Question 4

Choose the one alternative that best completes the statement or answers the question.
You are in a train traveling on a horizontal track and notice that a piece of luggage starts to slide directly toward the front of the train. From this observation, you can conclude that this train is

A) slowing down and changing direction.
B) changing direction.
C) speeding up and changing direction.
D) slowing down.
E) speeding up.

Question 5

Choose the one alternative that best completes the statement or answers the question.
A bucket is being lowered by a very light rope with a constant downward velocity. The tension in the rope must be

A) greater than the weight of the bucket.
B) less than the weight of the bucket.
C) equal to the weight of the bucket.

Question 6

Choose the one alternative that best completes the statement or answers the question.
Bill and his daughter Susan are both standing on identical skateboards (with really good frictionless ball bearings), initially at rest. Bill weighs three times as much as Susan. Bill pushes
Horizontally on Susan's back, causing Susan to start moving away from Bill. Just after Bill stops
Pushing,

A) Susan and Bill are moving away from each other, and Susan's speed is one-third that of Bill.
B) Susan and Bill are moving away from each other, with equal speeds.
C) Susan and Bill are moving away from each other, and Susan's speed is three times that of Bill.
D) Susan is moving away from Bill, and Bill is stationary.

Question 7

Choose the one alternative that best completes the statement or answers the question.
While flying horizontally in an airplane, you notice that a string dangling from the overhead luggage compartment hangs at rest at $15 ^ { \circ }$ away from the vertical toward the front of the plane.
Using this observation, you can conclude that the airplane is

A) not accelerating because the string is at rest.
B) moving forward.
C) accelerating forward.
D) moving backward.
E) accelerating backward.

Question 8

Choose the one alternative that best completes the statement or answers the question.
If you pound a feather with a hammer, which one feels a greater force?

A) If the feather moves, then it felt the greater force. Otherwise the force was the same on both.
B) always the feather
C) always the hammer
D) The size of the force is always exactly the same on both of them.

Question 9

Choose the one alternative that best completes the statement or answers the question.
An object is moving with constant non-zero velocity. Which of the following statements about it must be true?

A) A constant force is being applied to it in the direction opposite of motion.
B) Its acceleration is in the same direction as it velocity.
C) A constant force is being applied to it in the direction of motion.
D) A constant force is being applied to it perpendicular to the direction of motion.
E) The net force on the object is zero.

Question 10

Choose the one alternative that best completes the statement or answers the question.
In order to lift a bucket of concrete, you must pull up harder on the bucket than the bucket pulls
down on you.

Question 11

Choose the one alternative that best completes the statement or answers the question.
In a collision between a huge SUV and a small hybrid car, the SUV exerts a larger force on the hybrid than the hybrid exerts on the SUV.

A) True
B) False
C) It depends on whether the collision is a head-on collision or a rear-end collision.

Question 12

Choose the one alternative that best completes the statement or answers the question.
An elevator suspended by a vertical cable is moving downward but slowing down. The tension in the cable must be

A) less than than the weight of the elevator.
B) equal to the weight of the elevator.
C) greater than the weight of the elevator.

Question 13

Choose the one alternative that best completes the statement or answers the question.
In order to get an object moving, you must push harder on it than it pushes back on you.

Question 14

Choose the one alternative that best completes the statement or answers the question.
A girl attaches a rock to a string, which she then swings counter-clockwise in a horizontal circle. The string breaks at point P in the figure, which shows a bird's-eye view (as seen from above).
Which path (A-E) will the rock follow?

A) Path A
B) Path B
C) Path C
D) Path D
E) Path E

Question 15

Choose the one alternative that best completes the statement or answers the question.
You push on box G that is next to box H, causing both boxes to slide along the floor, as shown in the figure. The reaction force to your push is

A) the push of box G on box H
B) the acceleration of box G .
C) the push of box H on box G .
D) the push of box G against you.
E) the upward force of the floor on box G

Question 16

Choose the one alternative that best completes the statement or answers the question.
A box is placed on a table which rests on the floor. The box pushes on the table; the reaction force
to the box's push on the table is the table's push on the floor.

Question 17

Choose the one alternative that best completes the statement or answers the question.
A 20-ton truck collides with a 1500-lb car. Which of the following statements must be true?

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

Question 18

Choose the one alternative that best completes the statement or answers the question.
You pull on a crate with a rope. If the crate moves, the rope's pull on the crate must have been
larger than the crate's pull on the rope, but if the crate does not move, both of these pulls must
have been equal.

Question 19

Choose the one alternative that best completes the statement or answers the question.
A truck is using a hook to tow a car whose mass is one quarter that of the truck. If the force exerted by the truck on the car is 6000 N, then the force exerted by the car on the truck is

A) 1500 N.
B) 24000 N.
C) 12000 N.
D) 6000 N.
E) We need to know if the car is accelerating to answer this question.

Question 20

Choose the one alternative that best completes the statement or answers the question.
A small car and a large SUV are at a stoplight. The car has a mass equal to half that of the SUV, and the SUV can produce a maximum accelerating force equal to twice that of the car. When the
Light turns green, both drivers push their accelerators to the floor at the same time. Which vehicle
Pulls ahead of the other vehicle after a few seconds?

A) The car pulls ahead.
B) It is a tie.
C) The SUV pulls ahead.

Question 21

Choose the one alternative that best completes the statement or answers the question.
In the figure, a 10-lb weight is suspended from two spring scales, each of which has negligible weight. Which one of the following statements about the readings in the scales is true?

A) Each scale will read 5 lb.
B) The lower scale will read zero, the top scale will read 10 lb.
C) Each scale will show a reading between one and 10 lb, such that the sum of the two is 10 lb. However, exact readings cannot be determined without more information.
D) The top scale will read zero, the lower scale will read 10 lb.
E) None of these is true.

Question 22

Choose the one alternative that best completes the statement or answers the question.
Two blocks, A and B, are being pulled to the right along a horizontal surface by a horizontal 100-N pull, as shown in the figure. Both of them are moving together at a constant velocity of 2.0 m/s to
The right, and both weigh the same. Which of the figures below shows a correct free-body diagram of the horizontal forces acting on
The lower block, B?

A)
B)
C)
D)
E) None of these diagrams is correct.

Question 23

Choose the one alternative that best completes the statement or answers the question.
A person who normally weighs 700 N is riding in a rather swift elevator that is moving at a constant speed of 9.8 m/s. If this person is standing on a bathroom scale inside the elevator, what
Would the scale read?

A) 700 N
B) more than 700 N
C) less than 700 N
D) It could be more or less than 700 N, depending on whether the elevator is going up or down.

Question 24

Choose the one alternative that best completes the statement or answers the question.
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 the force on his
Hands equals his weight, what happens to the fireman?

A) The fireman comes to a stop.
B) The fireman descends with a smaller but non-zero acceleration.
C) The fireman descends with slower and slower speed.
D) The acceleration of the fireman is now upward.
E) The fireman continues to descend, but with constant speed.

Question 25

Choose the one alternative that best completes the statement or answers the question.
An object of mass m rests on a flat table. The earth pulls on this object with a force of magnitude mg . What is the reaction force to this pull?

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

Question 26

Choose the one alternative that best completes the statement or answers the question.
You are standing in a moving bus, facing forward, when you suddenly slide forward as the bus comes to an immediate stop. What force caused you to slide forward?

A) the force due to friction between you and the floor of the bus
B) the normal force due to your contact with the floor of the bus
C) gravity
D) There is not a force causing you to slide forward.

Question 27

Choose the one alternative that best completes the statement or answers the question.
A person is using a rope to lower a 5.0-N bucket into a well with a constant speed of 2.0 m/s. What is the magnitude of the force exerted by the rope on the bucket?

A) 0.00 N
B) 5.0 N
C) 10 N
D) 2.0 N
E) 49 N

Question 28

Choose the one alternative that best completes the statement or answers the question.
A person who normally weighs 700 N is riding in an elevator that is moving upward but slowing down at a steady rate. If this person is standing on a bathroom scale inside the elevator, what
Would the scale read?

A) 700 N
B) less than 700 N
C) more than 700 N
D) It could be more or less than 700 N, depending on whether the magnitude of the acceleration is greater than or less than 9.8 m/s².

Question 29

Choose the one alternative that best completes the statement or answers the question.
The figure shows two boxes, with $m 1 > m 2$ that are on a level frictionless surface. We can apply a horizontal force $\overrightarrow { \mathrm { F} }$ either toward the right on $m 1$ or toward the left on $m _ { 2 }$ The magnitude of the force that the boxes exert on each other is

A) larger if $\overrightarrow { \mathbf { F } }$ is applied toward the left.
B) the same in either case.
C) larger if $\overrightarrow { \mathbf { F } }$ is applied toward the right.
D) zero newtons in either case.

Question 30

Choose the one alternative that best completes the statement or answers the question.
Inside of a train a ball of weight W is hanging by a light wire at rest from the ceiling. The wire makes an angle θ with the ceiling, as shown in the figure. Which one of the following conditions
Must be true about the tension T in the wire?

A) $T \tan \theta = W$
B) $T \cos \theta = W$
C) T = W
D) T = ma
E) $T \sin \theta = W$

Question 31

Choose the one alternative that best completes the statement or answers the question.
Two blocks, A and B, are being pulled to the right along a horizontal surface by a horizontal 100-N pull, as shown in the figure. Both of them are moving together at a constant velocity of 2.0 m/s to
The right, and both weigh the same. Which of the figures below shows a correct free-body diagram of the horizontal forces acting on
The upper block, A?

A)
B)
(No horizontal forces act on $A$ .)
C) $A \longrightarrow 50 \mathrm {~N}$
D) $\mathrm{A} \longrightarrow 100 \mathrm{~N}$
E)

Question 32

Choose the one alternative that best completes the statement or answers the question.
A horse pulls a cart with force $\vec { F }$ As a result of this force the cart accelerates with constant acceleration. The magnitude of the force that the cart exerts on the horse

A) less than the magnitude of $\overrightarrow { \mathrm { F } }$
B) is zero newtons.
C) greater than the magnitude of $\vec { F }$
D) equal to the magnitude of $\overrightarrow { \mathrm { F } }$
E) cannot be determined without knowing the mass of the horse.

Question 33

Choose the one alternative that best completes the statement or answers the question.
A push of magnitude P acts on a box of weight W as shown in the figure. The push is directed at an angle $\theta$ below the horizontal, and the box remains a rest. The box rests on a horizontal surface that has some friction with the box. The normal force on the box due to the floor is equal to

A) W+P .
B) W .
C) $W - P \sin \theta$
D) $W + P \cos \theta$
E) $W + P \sin \theta$

Question 34

Choose the one alternative that best completes the statement or answers the question.
A golf club hits a golf ball with a force of 2400 N, sending the ball into the air. The force exerted on the club by the ball must be less than 2400 N or else the ball would not have moved forward.

A) True
B) False
C) The answer depends on whether the golfer followed through with the swing.

Question 35

Choose the one alternative that best completes the statement or answers the question.
When a 45-kg person steps on a scale in an elevator, the scale reads a steady 410 N. Which of the following statements must be true? (There could be more than one correct choice.)

A) The elevator is accelerating downward at a constant rate.
B) The elevator is moving downward at a constant rate.
C) The elevator is accelerating upward at a constant rate.
D) The elevator is moving upward at a constant rate.
E) From the given information, we cannot tell if the elevator is moving up or down.

Question 36

Choose the one alternative that best completes the statement or answers the question.
An object of weight W is in freefall close to the surface of Earth. The magnitude of the force that the object exerts on Earth is

A) cannot be determined without knowing the relative masses of the object and the earth.
B) equal to W.
C) less than W.
D) greater than W.
E) zero.

Question 37

Choose the one alternative that best completes the statement or answers the question.
The acceleration due to gravity is lower on the Moon than on Earth. Which one of the following statements is true about the mass and weight of an astronaut on the Moon's surface, compared to
Earth?

A) Both mass and weight are the same.
B) Both mass and weight are less.
C) Mass is less, weight is the same.
D) Mass is the same, weight is less.

Question 38

Choose the one alternative that best completes the statement or answers the question.
As shown in the figure, a woman is straining to lift a large crate, but without success because it is too heavy. We denote the forces on the crate as follows: P is the magnitude of the upward force
Being exerted on the crate by the person, C is the magnitude of the vertical contact force on the
Crate by the floor, and W is the weight of the crate. How are the magnitudes of these forces related
While the person is trying unsuccessfully to lift the crate?

A) P + C > W
B) P + C < W
C) P + C = W
D) P = C

Question 39

Choose the one alternative that best completes the statement or answers the question.
A 75-N box rests on a perfectly smooth horizontal surface. The minimum force need to start the box moving is

A) 75 N.
B) 750 N.
C) 7.5 N.
D) any horizontal force greater than zero.

Question 40

Choose the one alternative that best completes the statement or answers the question.
When a 45-kg person steps on a scale in an elevator, the scale reads a steady 480 N. Which of the following statements must be true? (There could be more than one correct choice.)

A) The elevator is moving downward at a constant rate.
B) The elevator is moving upward at a constant rate.
C) The elevator is accelerating downward at a constant rate.
D) The elevator is accelerating upward at a constant rate.
E) From the given information, we cannot tell if the elevator is moving up or down.

Question 41

Choose the one alternative that best completes the statement or answers the question.
In the figure, what does the spring scale read? The pulleys are ideal and the strings and scale are also massless.

A) more than 19.6 N
B) 0.00 N
C) 0.50 N
D) exactly 2.0 N
E) exactly 1.0 N

Question 42

Choose the one alternative that best completes the statement or answers the question.
A 200-N sled of slides down a frictionless hillside that rises at 3 bove the horizontal. What is the magnitude of the force that the surface of the hill exerts on the sled?

A) 0 N
B) 160 N
C) 120 N
D) 150 N
E) 200 N

Question 43

Choose the one alternative that best completes the statement or answers the question.
Two boxes are connected to each other by a string as shown in the figure. The 10-N box slides without friction on the horizontal table surface. The pulley is ideal and the string has negligible mass. What is true about the tension T in the string?

A) T<30 N
B) T=10 N
C) T=20 N
D) T>30 N
E) T=30 N

Question 44

Choose the one alternative that best completes the statement or answers the question.
An astronaut weighs 99 N on the Moon, where the acceleration of gravity is 1.62 m/s². How much does she weigh on Earth?

A) 99 N
B) 61 N
C) 600 N
D) 440 N
E) 16 N

Question 45

Choose the one alternative that best completes the statement or answers the question.
Two boxes, A and B , are connected by a horizontal string S on a horizontal floor. A very light wire pulls horizontally on box B, as shown in the figure, with a force of 100 N. The reaction force to this pull is

A) the pull that string S exerts on box A .
B) the force that box A exerts on box B .
C) the pull that box B exerts on string S.
D) the pull of box B on the wire.
E) the pull that string S exerts on box B.

Question 46

Choose the one alternative that best completes the statement or answers the question.
A block is on a frictionless table, on earth. The block accelerates at 3.0 m/s² when a 20 N horizontal force is applied to it. The block and table are set up on the Moon where the acceleration due to
Gravity is 1.62 m/s². The weight of the block on the Moon is closest to

A) 6.8 N.
B) 5.5 N.
C) 9.5 N.
D) 8.1 N.
E) 11 N.

Question 47

Choose the one alternative that best completes the statement or answers the question.
If a net force accelerates a 4.5-kg tool at 40 m/s², what acceleration would that same net force give to an 18-kg tool?

A) 9.8 m/s²
B) 160 m/s²
C) 10 m/s²
D) 32 m/s²
E) 180 m/s²

Question 48

Choose the one alternative that best completes the statement or answers the question.
A block is on a frictionless table, on earth. The block accelerates at 5.3 m/s² when a 10 N horizontal force is applied to it. The block and table are set up on the Moon where the acceleration due to
Gravity is 1.62 m/s². A horizontal force of 5 N is now applied to the block when it is on the Moon.
The acceleration imparted to the block by this force is closest to

A) 2.7 m/s².
B) 2.4 m/s².
C) 3.2 m/s².
D) 3.4 m/s².
E) 2.9 m/s².

Question 49

Choose the one alternative that best completes the statement or answers the question.
Two objects of unequal masses, M and m(M > m) , are connected by a very light cord passing over an ideal pulley of negligible mass. When released, the system accelerates, and friction is negligible.

Which one of the following free-body diagrams most realistically represents the forces acting on the two objects in the moving system?

A)
B)
C)
D)

Question 50

Choose the one alternative that best completes the statement or answers the question.
A push of magnitude P acts on a box of weight W as shown in the figure. The push is directed at an angle $\theta$ below the horizontal, and the box remains a rest. The box rests on a horizontal surface that has some friction with the box. The friction force on the box due to the floor is equal to

A) $P \cos \theta + W$
B) $P \cos \theta$
C) 0
D) $P \sin \theta$
E) P+W

Question 51

Write the word or phrase that best completes each statement or answers the question.
An object has a mass of 60 kg on Earth. What are the mass and weight of this object on
the surface of the Moon where the acceleration due to gravity is only 1/6 of what it is on
Earth?

Question 52

Choose the one alternative that best completes the statement or answers the question.
What is the mass of an object that experiences a gravitational force of 685 N near Earth's surface where g = 9.80 m/s²?

A) 72.7 kg
B) 69.9 kg
C) 68.5 kg
D) 71.3 kg

Question 53

Choose the one alternative that best completes the statement or answers the question.
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) 5.21 kg.
B) 2880 kg.
C) 144 kg.
D) 0.200 kg.
E) 3000 kg.

Question 54

Choose the one alternative that best completes the statement or answers the question.
Three boxes are pulled along a horizontal frictionless floor by a constant horizontal pull P . The boxes are connected by very light horizontal strings having tensions as shown in the figure. Which of the following statements about the tensions is correct? (There could be more than one correct choice.)

A)
B)
C)
D)
E)

Question 55

Choose the one alternative that best completes the statement or answers the question.
A block of mass m sits at rest on a rough inclined ramp that makes an angle with the horizontal. What must be true about force of static friction on the block?

A)
B)
C)
D)
E)

Question 56

Choose the one alternative that best completes the statement or answers the question.
If I weigh 741 N on Earth at a place where g = 9.80 m/s² and 5320 N on the surface of another planet, what is the acceleration due to gravity on that planet?

A) 61.2 m/s²
B) 70.4 m/s²
C) 81.0 m/s²
D) 51.4 m/s²

Question 57

Choose the one alternative that best completes the statement or answers the question.
A 200-N sled of slides down a frictionless hillside that rises at 37° above the horizontal. What is the magnitude of the force that the hill exerts on the sled parallel to the surface of the hill?

A) 0 N
B) 200 N
C) 120 N
D) 160 N
E) 150 N

Question 58

Choose the one alternative that best completes the statement or answers the question.
Two boxes P and Q on a perfectly smooth horizontal surface are connected by a light horizontal cord. The mass of P is greater than that of Q . A horizontal force $\overrightarrow { \mathbf { F } }$ is applied to box Q as shown in the figure, accelerating the bodies to the right. The magnitude of the force exerted by the connecting cord on body P is

A) greater than F .
B) less than F but not zero.
C) equal to F .
D) zero.

Question 59

Choose the one alternative that best completes the statement or answers the question.
Two objects have masses m and 5m, respectively. They both are placed side by side on a frictionless inclined ramp and allowed to slide down from rest without any air resistance. Which
One of the following statements about these objects is correct?

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

Question 60

Choose the one alternative that best completes the statement or answers the question.
A block of mass m sits at rest on a rough inclined ramp that makes an angle θ with the horizontal. What must be true about normal force F on the block due to the ramp?

A)
B)
C)
D)
E)

Question 61

Write the word or phrase that best completes each statement or answers the question.
During a hard stop, a car and its passengers slow down with an acceleration o What magnitude force does a 50-kg passenger exert on the seat belt in such a stop?

Question 62

Write the word or phrase that best completes each statement or answers the question.
A box of mass 72 kg is at rest on a horizontal frictionless surface. A constant horizontal
force of magnitude F then acts on the box, accelerating it to the right. You observe that it
takes the box 3.4 seconds to travel 13 meters. What is the magnitude of the force F?

Question 63

Choose the one alternative that best completes the statement or answers the question.
On its own, a tow truck has a maximum acceleration of 3.0 m/s². What will be its maximum acceleration when the truck is using a light horizontal chain to tow a bus of twice its own mass?

A) 2.0 m/s²
B) 1.5 m/s²
C) 1.0 m/s²
D) 2.5 m/s²

Question 64

Choose the one alternative that best completes the statement or answers the question.
A 1200-kg car is pulling a 500-kg trailer along level ground. Friction of the road on the trailer is negligible. The car accelerates with an acceleration o What is the force exerted by the car
On the trailer?

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

Question 65

Choose the one alternative that best completes the statement or answers the question.
A 450-kg sports car accelerates from rest to 100 km/h in 4.80 s. What magnitude force does a 68.0 kg passenger experience during the acceleration?

A) 311 N
B) 342 N
C) 82.0 N
D) 394 N

Question 66

Write the word or phrase that best completes each statement or answers the question.
In a certain particle accelerator, a proton reaches an acceleration of . The
mass of a proton is 1 . What is the force on the proton?

Question 67

Write the word or phrase that best completes each statement or answers the question.
A 40-kg crate is being lowered with a downward acceleration is 2.0 m/s² by means of a
rope.
(a) What is the magnitude of the force exerted by the rope on the crate?
(b) What would be the magnitude of the force exerted by the rope if the crate were being
raised with an acceleration of 2.0 m/s²?

Question 68

Choose the one alternative that best completes the statement or answers the question.
An object that weighs 75 N is pulled on a horizontal surface by a horizontal pull of 50 N to the right. The friction force on this object is 30 N to the left. What is the acceleration of the object?

A)
B)
C)
D)

Question 69

Choose the one alternative that best completes the statement or answers the question.
What magnitude net force is required to accelerate a 1200-kg car uniformly from 0 m/s to 27.0 m/s in 10.0 s?

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

Question 70

Write the word or phrase that best completes each statement or answers the question.
A 590-kg rocket is at rest on the launch pad. What upward thrust force is needed to
accelerate the rocket uniformly to an upward speed of 28 m/s in 3.3 s?

Question 71

Choose the one alternative that best completes the statement or answers the question.
A certain 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 a constant 445,000 N, what is the speed of the airplane 10.0 s later?

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

Question 72

Choose the one alternative that best completes the statement or answers the question.
A 45.0-kg person steps on a scale in an elevator. The scale reads 460 N. What is the magnitude of the acceleration of the elevator?

A)
B)
C)
D)
E)

Question 73

Write the word or phrase that best completes each statement or answers the question.
A catcher stops a 0.15-kg ball traveling at 40 m/s in a distance of 20 cm. What is the
magnitude of the average force that the ball exerts against his glove?

Question 74

Choose the one alternative that best completes the statement or answers the question.
Calculate the average force a bumper would have to exert to bring a 1200-kg car to rest in 15 cm when the car had an initial speed of 2.0 m/s (about 4.5 mph).

A)
B)
C)
D)
E)

Question 75

Write the word or phrase that best completes each statement or answers the question.
A flatbed truck is carrying an 800-kg load of timber that is not tied down. The maximum
friction force between the truck bed and the load is 2400 N. What is the greatest
acceleration that the truck can have without losing its load?

Question 76

Choose the one alternative that best completes the statement or answers the question.
The figure shows an object's acceleration-versus-force graph. What is the mass of this object?

A) 2.5 g
B) 400,000 g
C) 1.6 g
D) 630 g

Question 77

Write the word or phrase that best completes each statement or answers the question.
A 958-N rocket is coming in for a vertical landing. It starts with a downward speed of 25
m/s and must reduce its speed to 0 m/s in 8.0 s for the final landing.
(a) During this landing maneuver, what must be the thrust due to the rocket's engines?
(b) What must be the direction of the engine thrust force?

Question 78

Write the word or phrase that best completes each statement or answers the question.
A 10-kg object is hanging by a very light wire in an elevator that is traveling upward. The
tension in the rope is measured to be 75 N. What are the magnitude and direction of the
acceleration of the elevator?

Question 79

Choose the one alternative that best completes the statement or answers the question.
A car of mass 1100 kg that is traveling at 27 m/s starts to slow down and comes to a complete stop in 578 m. What is the magnitude of the average braking force acting on the car?

A) 410 N
B) 690 N
C) 550 N
D) 340 N

Question 80

Choose the one alternative that best completes the statement or answers the question.
The figure shows an acceleration-versus-force graph for a 125-g object. What should be the value of the first tick-mark on the vertical scale, as indicated by the arrow in the figure?

A) 0.00800
B) 0.00400
C) 8
D) 4