Physics Final

Question 1

1. In the product A ∙ B ∙ C, A has 5 significant figures, B has 4 significant figures, and C has 3 significant
   figures. How many significant figures does the product have? a. 2
   b. 3
   c. 4
   d. 5

Answer 1

3

Question 2

How many significant figures are in the number 0.0047010?

Answer 2

5

Question 3

3. Two displacement vectors have magnitudes of 5.0 m and 7.0 m, respectively. If these two vectors are
   added together, the magnitude of the sum. a. is equal to 2.0 m.
   b. could be as small as 2.0 m or as large as 12 m.
   c. is equal to 12 m.
   d. is equal to 8.6 m.

Answer 3

b

Question 4

onsider two vectors and shown in the figure. The difference A-B is best illustrated by

Answer 4

graph c (upward pointing arrow to left)

Question 5

5. A volume of 1000 mL is equivalent to which one of the following volumes? a. 1 kL
   b. 1 x 10-6 μL
   c. 1 x 10^0 L
   d. 0.01 ML

Answer 5

c

Question 6

A water fountain provides 1700. mL of water per minute. How many gal/sec is this? (1 gal = 3.78 L) a. 7.50 x 10-3 gal/sec
b. 0.107 gal/sec
c. 0.259 gal/sec
d. 386 gal/sec

Answer 6

a

Question 7

7. Rock X is released from rest at the top of a cliff that is on Earth. A short time later, Rock Y is released
   from rest from the same location as Rock X. Both rocks fall for several seconds before landing on the
   ground directly below the cliff. Frictional forces are considered to be negligible. Which of the
   following graphs correctly shows the vertical velocity of rock X as a function of time? Take the
   positive direction to be upward.

Answer 7

graph that stays negative the whole time in a straight line

Question 8

A ball is thrown straight up in the air. When the ball reaches its highest point, which of the following
is true? a. It is in equilibrium.
b. It has zero acceleration.
c. It has maximum potential energy.
d. It has maximum kinetic energy.

Answer 8

c

Question 9

A block is projected up a frictionless plane with an initial speed vo. The plane is inclined 30° above the
horizontal. What is the approximate acceleration of the block at the instant that it reaches its highest
point on the inclined plane?
a. Zero
b. 5 m/s2 down the incline
c. 10 m/s2 down the incline
d. 10 m/s2 up the incline

Answer 9

b

Question 10

A ball is thrown horizontally from the top of a tower at the same instant that a stone is dropped
vertically. Which object is traveling faster when it hits the level ground below if neither of them
experiences any air resistance?
a. It is impossible to tell because we do not know their masses.
b. the stone
c. the ball
d. Both are traveling at the same speed.

Answer 10

c

Question 11

In an air-free chamber, a pebble is thrown horizontally, and at the same instant a second pebble is
dropped from the same height. Compare the times of fall of the two pebbles.
a. The thrown pebble lands first.
b. The dropped pebble lands first.
c. They land at the same time.
d. We cannot tell without knowing which pebble is less massive.

Answer 11

c

Question 12

Which of the following situations is impossible?
a. An object has velocity directed east and acceleration directed west.
b. An object has zero velocity but non-zero acceleration.
c. An object has constant non-zero acceleration and changing velocity.
d. An object has constant non-zero velocity and changing acceleration.

Answer 12

d

Question 13

A small cart is rolling freely on an inclined ramp with a constant acceleration of 0.50 m/s2
in the -
x direction. At time t = 0, the cart has a velocity of 2.0 m/s in the +x-direction. If the cart never leaves
the ramp, which of the following statements correctly describes the motion of the cart at a time t > 5 s?
a. The cart is traveling in the +x-direction and is slowing down.
b. The cart is traveling in the +x-direction and is speeding up.
c. The cart is traveling in the –x-direction and is slowing down.
d. The cart is traveling in the –x-direction and is speeding up.

Answer 13

d

Question 14

A racquetball strikes a wall with a speed of 30 m/s and rebounds in the opposite direction with a speed
of 26 m/s. The collision takes 20 ms. What is the average acceleration of the ball during the collision
with the wall?
a. 1500 m/s2
b. 2800 m/s2
c. 5600 m/s2
d. 12000 m/s2

Answer 14

b

Question 15

The graph represents position x versus time t for an object being acted on by a constant force. The
average speed during the interval between 1 s and 2 s is most nearly
a. 2 m/s
b. 4 m/s
c. 5 m/s
d. 6 m/s

Answer 15

d

Question 16

an object is sliding to the right along a straight line on a horizontal surface. The graph shows the
object’s velocity as a function of time. What is the object’s displacement during the time depicted in
the graph?
a. 0 m
b. 1 m
c. 8 m
d. 16 m

Answer 16

a

Question 17

A student is provided with a battery-powered toy car that the manufacturer claims will always operate
at a constant speed. The student must design an experiment in order to test the validity of the claim.
Which of the following measuring tools can the student use to test the validity of the claim? Select two
answers.
a. Photogates placed at the beginning, end, and at various locations along the track that the car
travels
b. A meterstick to measure the distance of the track that the car travels
c. A motion detector that is oriented perpendicular to the direction that the car travels
d. A mass balance to determine the mass of the car

Answer 17

a (a and b if asked for two)

Question 18

which of the following graphs represent an object having zero acceleration?
a. only graph a
b. only graph b
c. graphs a and b
d. graphs b and d

Answer 18

c

Question 19

An object travels along a straight, horizontal surface with an initial speed of 2 m/s. The velocity of the
object as a function of time is given in the table above. Which of the following graphs represents the
object’s acceleration as a function of time?

Answer 19

a (acceleration in a straight line)

Question 20

he slope at a point on a position-versus-time graph of an object is
a. The object’s speed at that point.
b. The object’s velocity at that point.
c. The object’s acceleration at that point.
d. The distance traveled by the object to that point.

Answer 20

b

Question 21

21. A graph of velocity versus time for a hockey puck shot into a goal appears as follows:
    Which of the following position graphs matches the velocity graph?

Answer 21

d (looks opposite to original almost)

Question 22

Masses P and Q move with the position graphs shown. Do P and Q ever have the same velocity? If so,
at what time or times?
a. P and Q have the same velocity at 2 s.
b. P and Q have the same velocity at 1 s and 3 s.
c. P and Q have the same velocity at 1 s, 2 s, and 3 s.
d. P and Q never have the same velocity.

Answer 22

a

Question 23

A student performs an experiment in which the horizontal position of a toy car is recorded on ticker
tape from a device that places dots on the tape in equal time intervals. The series of dots in the figure
represents the motion of an object moving from the negative direction to the positive direction along
the horizontal direction. The time interval between each recorded dot is 1s. Which of the following
experiments could the student have conducted to create the data shown on the ticker tape?
a. A toy car that initially increases its speed, travels at a constant speed, and then increases its
speed again.
b. A toy car that initially increases its speed, travels at a constant speed, and then decreases its
speed.
c. A toy car that initially decreases its speed, stops, and then increases its speed.
d. A toy car that initially decreases its speed, travels at a constant speed, and then increases its
speed.

Answer 23

b

Question 24

an object is held at an unknown height above Earth’s surface. After the object is released from rest, a
student must determine the object’s speed the instant the object makes contact with the ground. Which
of the following equations could the student use to determine the object’s speed by using the fewest
measuring tools if the student does not have access to a motion sensor? Select two answers.
a. v = v0+at
b. x = x0+v0t+1/2 at2
c. v2 = v02+2a(x−x0)
d. v = (x−x0)/t

Answer 24

a, c

Question 25

An airplane travels at 300 mi/h south for 2.00 h and then at 250 mi/h north for 750 miles. What is the
average speed for the trip?
a. 260 mi/h
b. 270 mi/h
c. 275 mi/h
d. 280 mi/h

Answer 25

b

Question 26

A student uses a motion sensor to collect data of the velocity of an object as a function of time during two
experimental trials, as shown. In which trial does the object have the greatest magnitude of acceleration, and in
which trial does the object travel the greatest distance?
Greatest Magnitude of Acceleration Greatest Distance
a. Trial 1 Trial 1
b. Trial 1 Trial 2
c. Trial 2 Trial 1
d. Trial 2 Trial 2

Answer 26

c

Question 27

An object moving in the -x direction experiences an acceleration of +2.0 m/s2. This means the object
a. travels 2.0 m in every second.
b. is traveling at 2.0 m/s.
c. is decreasing its velocity by 2.0 m/s every second.
d. is increasing its velocity by 2.0 m/s every second.

Answer 27

c

Question 28

A cart with an initial velocity of 5.0 m/s to the left experiences a constant acceleration of 2.0 m/s2
to
the right. What is the cart’s displacement during the first 6.0 s of this motion?
a. 6 m
b. 55 m
c. 66 m
d. 80 m

Answer 28

a

Question 29

The graph in the figure shows the position of a particle as it travels along the x-axis. At what value of t
is the speed of the particle equal to 0 m/s?
a. 0 s
b. 1 s
c. 2 s
d. 3 s

Answer 29

d

Question 30

The area under a curve in a velocity versus time graph gives
a. acceleration.
b. velocity.
c. displacement.
d. position.

Answer 30

c

Question 31

31. The motion of a particle is described in the velocity vs. time graph shown in the figure. Over the ninesecond interval shown, we can say that the speed of the particle.
    a. only increases.
    b. only decreases.
    c. increases and then decreases.
    d. decreases and then increases.

Answer 31

d

Question 32

A ball traveling at a speed νo rolls off a desk and lands at a horizontal distance x away from a lab table.
The ball is then rolled off of the same table at a speed of 3 νo. At what horizontal distance will the ball
land from the table?
a. x
b. √3𝑥
c. 2x
d. 3x

Answer 32

d

Question 33

A student throws a rock horizontally from the edge of a cliff that is 20 m high. The rock has an initial
horizontal speed of 10 m/s. If air resistance is negligible, the distance from the base of the cliff to
where the rock hits the level ground below the cliff is most nearly
a. 5 m
b. 10 m
c. 20 m
d. 40 m

Answer 33

c

Question 34

A pilot drops a package from a plane flying horizontally at a constant speed. Neglecting air resistance,
when the package hits the ground the horizontal location of the plane will
a. be behind the package.
b. be directly over the package.
c. be in front of the package.
d. depend on the speed of the plane when the package was released.

Answer 34

b

Question 35

You throw a rock horizontally off a cliff with a speed of 20 m/s and no significant air resistance. After
2.0 s, the magnitude of the velocity of the rock is closest to
a. 28 m/s
b. 20 m/s
c. 40 m/s
d. 37 m/s

Answer 35

a

Question 36

girl throws a ball with an initial velocity of 25 m/s at an angle of 30° above the horizontal. If air
resistance is negligible, how high above the projection point is the ball after 2.0 s?
a. 5.4 m
b. 13 m
c. 25 m
d. 43 m

Answer 36

a

Question 37

Suppose a ball is thrown straight up and experiences no appreciable air resistance. What is its
acceleration just before it reaches its highest point?
a. slightly less than g
b. exactly g
c. slightly greater than g
d. zero

Answer 37

b

Question 38

A boy kicks a football from ground level with an initial velocity of 20 m/s at an angle of 30° above the
horizontal. What is the horizontal distance to the point where the football hits the ground if we neglect
air resistance?
a. 20 m
b. 35 m
c. 18 m
d. 60 m

Answer 38

b

Question 39

An object of mass 10. kg is released from rest above the surface of a planet such that the object’s speed
as a function of time is shown by the graph above. The force due to gravity exerted on the object is
most nearly
a. 3.5  N
b. 7.0  N
c. 35 N

Answer 39

c

Question 40

The sum of the forces on the object is zero in which of the cases?
a. II only
b. III only
c. I and II only
d. I and III only

Answer 40

c

Question 41

41. A bucket is being lowered by a very light rope with a constant downward velocity. The tension in the
    rope must be
    a. equal to the weight of the bucket.
    b. greater than the weight of the bucket.
    c. less than the weight of the bucket.

Answer 41

a

Question 42

A person is running on a track. Which of the following forces propels the runner forward?
a. The normal force exerted by the ground on the person
b. The normal force exerted by the person on the ground
c. The force of friction exerted by the ground on the person
d. The force of friction exerted by the person on the ground

Answer 42

c

Question 43

To analyze the characteristics and performance of the brakes on a 1500 kg car, researchers collected
the data shown in the table. It shows the car’s speed when the brakes are first applied and the
corresponding braking distance required to stop the car. The magnitude of the average braking force on
the car is most nearly
a. 75,000 N
b. 30,000 N
c. 12,000 N
d. 1600 N

Answer 43

c

Question 44

An elevator carrying a person of mass m is moving upward and slowing down. How does the
magnitude F of the force exerted on the person by the elevator floor compare with the magnitude mg
of the gravitational force?
a. F < mg
b. F = mg
c. F > mg
d. F can be greater than or less than mg, depending on the speed of the elevator.

Answer 44

a

Question 45

a ball is dropped onto the floor and bounces upward. Which of the following claims are correct about
the force that the ball exerts on the floor compared to the force that the floor exerts on the ball when
the ball and the floor are in contact?
a. The ball exerts a greater force on the floor because the ball travels with a high speed, whereas
the floor is at rest.
b. The ball exerts a greater force on the floor because the ball is accelerating.
c. The magnitude of the forces exerted by both objects is the same because the ball and the floor
cannot exert forces of different magnitudes on each other.
d. The magnitude of the forces exerted by both objects is the same because the gravitational force
exerted by the ball on the floor and the gravitational force exerted on the floor by the ball must
be the same.

Answer 45

c

Question 46

An object is moving with constant non-zero velocity. Which of the following statements about it must
be true?
a. The net force on the object is zero.
b. A constant force is being applied to it in the direction of motion.
c. Its acceleration is in the same direction as its velocity.
d. The force of friction is equal to the normal force.

Answer 46

a

Question 47

Students work together during an experiment about Newton’s laws. The students use a setup that consists of a
cart of known mass connected to one end of a string that is looped over a pulley of negligible friction, with its
other end connected to a hanging mass. The cart is initially at rest on a horizontal surface and rolls without
slipping when released. The inertia of the cart’s wheels is negligible. Students have access to common
laboratory equipment to make measurements of components of the system.
47. By collecting the appropriate data, the students can determine the relationship between the acceleration
of the cart and the net force exerted on the cart. Which of the following graphs should the students
produce to show the correct relationship?

Answer 47

a (diagonal line from zero up)

Question 48

The students double the mass that hangs from the string. They also replace the original cart with a new
cart that has double the mass. By doubling both masses, how will the tension in the string and the
acceleration of the cart change?
a. The tension and the acceleration will double.
b. The tension will double, but the acceleration will stay the same.
c. The tension will stay the same, but the acceleration will double.
d. The tension and the acceleration will stay the same.

Answer 48

b

Question 49

49. Block X of mass M is attached to block Y of mass 2M by a light string that passes over a pulley of
    negligible friction and mass, as shown above. In which direction will the center of mass of the twoblock system move after it is released from rest, and what is the magnitude of the acceleration a of
    block X ?
    Center of Mass a
    a. Down and to the right 2g/3
    b. At rest 2g/3
    c. Down and to the right 3g/2
    d. At rest 3g/2

Answer 49

a

Question 50

An Atwood’s machine is set up by suspending two blocks connected by a string of negligible mass
over a pulley, as shown above. The blocks are initially held at rest and then released at time t0 = 0 The
speed of the 3 kg block at time t = 2.0s is most nearly
a. 2.0  m/s
b. 4.0 m/s
c. 7.0 m/s
d. 10.0 m/s

Answer 50

b

Question 51

The table shows experimental data of the magnitude of four forces exerted on a 2kg object as it slides
across a horizontal surface. Which of the following could represent the magnitude of the net force that
is exerted on the object? Select two answers.
a. 6N
b. 10N
c. 28N
d. 30N

Answer 51

a,b

Question 52

The free body diagram shown is for a 5 kg box on a rough surface being pulled to the right at a
constant speed by a string that is at an angle of 30°above the horizontal. The coefficient of kinetic
friction between the box and the surface is 0.30. The tension in this string is most nearly
a. 14.5 N
b. 17.0 N
c. 20.5 N
d. 29.4 N

Answer 52

a

Question 53

n order to get an object moving, you must push harder on it than it pushes back on you.
a. True
b. False

Answer 53

b

Question 54

54. 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 sin θ = W
    b. T cos θ = W
    c. T tan θ = W
    d. T = W

Answer 54

a

Question 55

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. 690 N
b. 550 N
c. 410 N
d. 340 N

Answer 55

a

Question 56

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 surface of the hill exerts on the sled?
a. 120 N
b. 150 N
c. 160 N
d. 200 N

Answer 56

c

Question 57

he figure shows a block of mass M hanging at rest. The light wire fastened to the wall is horizontal
and has a tension of 38 N. The wire fastened to the ceiling has a tension of and makes an angle θ
with the ceiling. Find the angle θ.
a. 33°
b. 40°
c. 45°
d. 50°

Answer 57

d

Question 58

A falling skydiver opens his parachute. A short time later, the weight of the skydiver-parachute system
and the drag force exerted on the system are equal in magnitude. Which of the following statements
predicts the motion of the skydiver at this time?
a. The skydiver is at rest.
b. The skydiver is moving downward with constant speed.
c. The skydiver is moving downward with an upward acceleration.
d. The skydiver is moving downward with a downward acceleration.

Answer 58

b

Question 59

In a floor hockey game, the puck slides a total of 12 m on a horizontal surface before coming to rest. If
the coefficient of kinetic friction between the puck and floor is 0.10, what was the initial speed of the
puck?
a. 3.8 m/s
b. 4.3 m/s
c. 4.8 m/s
d. 5.5 m/s

Answer 59

c

Question 60

A 1 kg block is placed near the top of an inclined plane that is at an angle of 30 degrees with respect to
the ground, as shown above. By correctly determining the effect of gravity, a student predicts that the
acceleration of the block will be 5 m/s2
. After allowing the block to slide down the inclined plane, the
student finds that the acceleration is actually 4 m/s2
. What type of force did the student most likely not
account for when predicting the acceleration of the block, and what is the magnitude of that force?
a. Force of friction of approximately 0.1 newtons
b. Force of friction of approximately 1 newton
c. Normal force of approximately 0.1 newtons
d. Normal force of approximately 1 newton

Answer 60

b

Question 61

the figure shows two crates, each of mass m = 24 kg, that are connected by a very light wire. The
coefficient of kinetic friction between the crate on the inclined surface and the surface itself is 0.31.
Find the speed of the crates after they have moved 1.6 m starting from rest.
a. 1.9 m/s
b. 2.7 m/s
c. 11 m/s
d. 14 m/s

Answer 61

a

Question 62

A rubber ball with mass 0.20 kg is dropped vertically from a height of 1.5 m above a floor. The ball
bounces off of the floor, and during the bounce 0.60 J of energy is dissipated. What is the maximum
height of the ball after the bounce?
a. 0.30 m
b. 0.90 m
c. 1.2 m
d. 1.5 m

Answer 62

c

Question 63

A sled slides down a hill with friction between the sled and hill but negligible air resistance. Which of
the following must be correct about the resulting change in energy of the sled-Earth system?
a. The sum of the kinetic energy and the gravitational potential energy changes by an amount
equal to the energy dissipated by friction.
b. The gravitational potential energy decreases and the kinetic energy is constant.
c. The decrease in the gravitational potential energy is equal to the increase in kinetic energy.
d. The gravitational potential energy and the kinetic energy must both decrease.

Answer 63

a

Question 64

Inertia can best be described as the
a. force that keeps an object in motion at a constant velocity.
b. force that keeps an object at rest.
c. property that is responsible for resistance to changes in motion.
d. property that is responsible for slowing an objects motion.

Answer 64

c

Question 65

a student is asked to determine the work done on a block of wood when the block is pulled
horizontally using an attached string. The student is supplied with a spring scale, a stopwatch, and a
meterstick. Which of the following graphical analysis techniques will allow the student to determine
the work done on the block by the string?
a. Graphing the force as a function of time and calculating the slope
b. Graphing the force as a function of time and calculating the area under the curve
c. Graphing the force as a function of distance and calculating the slope
d. Graphing the force as a function of distance and calculating the area under the curve

Answer 65

d

Question 66

A block is pushed along a horizontal frictionless surface with a horizontal force that varies with time
as shown in the graph. At time t = 3 sec the acceleration is 5.0 m/s2
. The mass of the block is
a. 3 kg
b. 5 kg
c. 15 kg
d. 45 kg

Answer 66

a

Question 67

A student uses a spring scale to exert a horizontal force on a block, pulling the block over a smooth
floor. The student repeats the procedure several times, each time pulling the block from rest through a
distance of 1.0 m. For which of the following graphs of force as a function of distance will the block
be moving the fastest at the end of the 1.0 m?

Answer 67

c

Question 68

A block of mass M is released from rest at point 1, as shown in the figure. The block slides without
frictional forces along the circular arc but encounters frictional forces as soon as it reaches the
horizontal portion of the track at point 2. The block travels a distance D along the horizontal track
before coming to rest at point 3. Consider the block-Earth system. In terms of the mechanical energy
of the system, which of the following claims is correct, and why?
a. The system is open, because there is a net force exerted on the block.
b. The system is open, because the block’s velocity is zero at points 1 and 3.
c. The system is closed, because there is a net force exerted on the block.
d. The system is closed, because the block’s velocity is zero at points 1 and 3.

Answer 68

a

Question 69

Which requires more work, increasing a car’s speed from 0 mph to 30 mph or from 50 mph to 60 mph?
a. 0 mph to 30 mph
b. 50 mph to 60 mph
c. It is the same in both cases.
d. Impossible to tell with this information.

Answer 69

b

Question 70

An inclined track is secured to a table. The height of the highest point of the track above the tabletop
is h1. The height from the tabletop to the floor is h2. A block of mass M is released from rest and slides
down the track such that all frictional forces are considered to be negligible. The block leaves the track
horizontally and strikes the ground at a distance D from the edge of the track as shown. Which of the
following statements is correct about the scenario? Select two answers.
a. The total mechanical energy of the system containing only the block increases from the
moment of release to the moment it strikes the ground.
b. The total mechanical energy of the block-Earth system remains constant.
c. If the block is released from a height 2h1, the block will land at a distance 2D away from the
end of the track.
d. If the block’s mass is increased to 2M, the block will land at a distance 2D away from the edge
of the track.

Answer 70

a, b

Question 71

A student collects the data necessary to graph the object’s kinetic energy as a function of time, as
shown. Which of the following graphs represents the sum of the kinetic energy K and gravitational
potential energy Ug of the object-Earth system as a function of time?

Answer 71

d (straight line across)

Question 72

A truck has four times the mass of a car and is moving with twice the speed of the car. If Kt and Kc
refer to the kinetic energies of truck and car respectively, it is correct to say that
a. Kt = 16Kc.
b. Kt = 4Kc.
c. Kt = Kc.
d. Kt = Kc.

Answer 72

a

Question 73

A block of mass m is launched by a spring of negligible mass along a horizontal surface of negligible
friction. The spring constant of the spring is k. The spring is initially compressed a distance xo. The
block is released from rest. Some time after the block is released and travels in the direction shown in
the figure, the spring compression is xf.. Which of the following mathematical calculations can a
student use to determine the speed vf of the block at this new position?
a. ½ k xi^2 = ½ mvf^2. Solve for vf .
b. ½ k xi^2 = ½ k xf ^2 + ½ mvf^2. Solve for vf .
c. Fcosθ xo = ½ mΔv^2. Solve for Δv.
d. F=Δxcosθ and F=mΔv/Δt. Solve f

Answer 73

b

Question 74

You slam on the brakes of your car in a panic, and skid a certain distance on a straight level road. If
you had been traveling twice as fast, what distance would the car have skidded, under the same
conditions?
a. It would have skidded 4 times farther.
b. It would have skidded twice as far.
c. It would have skidded 1.4 times farther.
d. It would have skidded one half as far.

Answer 74

a

Question 75

When you throw a pebble straight up with initial speed v, it reaches a maximum height H with no air
resistance. At what speed should you throw it up vertically so it will go twice as high?
a. square root v
b. 1/2 v
c. 2v
d. 4v

Answer 75

a

Question 76

A 5 kg object near Earth’s surface is released from rest such that it falls a distance of 10 m. After the
object falls 10 m, it has a speed of 12 m/s. Which of the following correctly identifies whether the
object-Earth system is open or closed and describes the net external force?
a. The system is closed, and the net external force is zero.
b. The system is open, and the net external force is zero.
c. The system is closed, and the net external force is nonzero.
d. The system is open, and the net external force is nonzero.

Answer 76

d

Question 77

A heavy dart and a light dart are launched vertically by identical ideal springs. Both springs were
initially compressed by the same amount. There is no significant air resistance. Which of the following
statements about these darts are correct? Select two answers.
a. The heavy dart goes higher than the light dart.
b. The light dart goes higher than the heavy dart.
c. Both darts reach the same maximum height.
d. At the maximum height, both darts have the same gravitational potential energy.

Answer 77

b, d

Question 78

A student must determine the effect of friction on the mechanical energy of a small block as it slides up a
ramp. The block is launched with an initial speed vo from point A along a horizontal surface of negligible
friction. It then slides up a ramp, where friction is not negligible, that is inclined at angle θ with respect to the
horizontal, as shown in the figure. The student measures the maximum vertical height h attained by the block
while on the ramp, labeled as point B in the figure. At point B, the block comes to rest. The student performs
three trials with the ramp at different angles, launching the block at the same initial speed vo for each trial. The
results from the trials are displayed in the table.
78. How should the student use the data collected and the known quantities from the experiment to
determine the initial total mechanical energy of the block-ramp-Earth system for all trials in the
experiment?
a. Use ΔE = W = F||d for all trials because the block traveled a different distance up the ramp in
each trial.
b. Use ΔUg = mgΔy for all trials because the block reaches a different height above the ground in
each trial.
c. Use WFf = Ugf for one trial because the same amount of work was done by the force of friction
in each trial.
d. Use K = 1/2mv2 with the block’s initial speed for one trial because the initial speed is the same
in all trials.

Answer 78

d

Question 79

Using the information from the prior problem, consider the trial with the 45°ramp. Suppose the block
is launched up the ramp such that it comes to rest at point B and then travels down the ramp. Which of
the following best describes the block’s kinetic energy KA when it again reaches point A at the bottom
of the ramp in comparison to the initial kinetic energy K0 before it travels up the ramp?
a. KA>K0, because the object will have a higher speed at the bottom of the ramp after sliding
down the ramp than its original launch speed.
b. KA<K0, because the force of friction removes mechanical energy from the block-ramp-Earth
system on its way up the ramp and back down the ramp.
c. KA=K0, because the law of the conservation of energy states that mechanical energy must be
conserved for a closed system.
d. It is impossible to predict how the kinetic energy of the block at point A will compare to the
original kinetic energy without knowing the magnitude of the force of friction that is exerted
on the block as it travels up and back down the ramp.

Answer 79

b

Question 80

A 100-N force has a horizontal component of 80 N and a vertical component of 60 N. The force is
applied to a cart on a level frictionless floor. The cart starts from rest and moves 2.0 m horizontally
along the floor due to this force. What is the cart’s final kinetic energy?
a. 200 J
b. 160 J
c. 120 J
d. Zero

Answer 80

b

Question 81

81. A force produces power P by doing work W in a time T. What power will be produced by a force that
    does six times as much work in half as much time?
    a. 12P
    b. 6P
    c. P
    d. P
    e. P

Answer 81

a

Question 82

A toy car has an initial acceleration of 2 m/s2
across a horizontal surface after it is released from rest.
After the car travels for a time t = 5 seconds, the speed of the car is 25m/s. Is the system consisting of
only the car an open system or a closed system, and why?
a. Open system, because the acceleration of the car is not constant.
b. Open system, because an external force is applied to the car that causes it to accelerate.
c. Closed system, because the speed of the car is as expected in the case where an object has
uniform acceleration for a time t.
d. Closed system, because mechanical energy was not removed from the system as a result of a
net force.

Answer 82

b

Question 83

The graphs shown show the magnitude F of the force exerted by a spring as a function of the distance
x the spring has been stretched. For which one of the graphs does the spring obey Hooke’s law?
a. Graph a
b. Graph b
c. Graph c
d. Graph d
e. Graph e

Answer 83

b

Question 84

A 5 kg block moves with a constant speed of 10 m/s to the right on a smooth surface where frictional
forces are considered to be negligible. It passes through a 2.0 m rough section of the surface where
friction is not negligible, and the coefficient of kinetic friction between the block and the rough
section μk is 0.20. What is the change in the kinetic energy of the block as it passes through the rough
section?
a. 20 Joules of energy are removed from the block.
b. 250 Joules of energy are removed from the block.
c. 20 Joules of energy are added to the block.
d. 250 Joules of energy are added to the block.

Answer 84

a

Question 85

A student uses a motion detector to record the speed of a 2kg object as a function of time as it travels
across a horizontal surface of negligible friction. Data from the experiment are shown in the graph. In
addition to the known mass, how can a student use the graph to determine the work done on the object
from 0s to 5s?
a. Use K=1/2mv2 with v equal to the speed of the object at 5s.
b. Use K=1/2mv2 with v equal to the average speed of the object.
c. Use ΔK=1/2mΔv2 with v0 equal to the speed of the object at 0s and vf equal to the speed of the
object at 5s.
d. A graph of the force exerted on the object as a function of time is required to determine the
work done on the object.

Answer 85

c

Question 86

A cart is moving with a speed of 20 m/s at position A on the track shown in the figure. This track is
friction-free, and there is no appreciable air resistance. What is the speed of the cart at point C?
a. 20 m/s
b. 34 m/s
c. 69 m/s
d. We cannot solve this problem without knowing
the mass of the bead.

Answer 86

b

Question 87

A 30-N stone is dropped from a height of 10 m and strikes the ground with a speed of 13 m/s. What
average force of air friction acted on the stone as it fell?
a. 2.9 N
b. 4.1 N
c. 130 N
d. 300 N

Answer 87

b

Question 88

What is the net power needed to change the speed of a 1600-kg sport utility vehicle from 15.0 m/s to
40.0 m/s in 4.00 seconds?
a. 100 kW
b. 10.0 kW
c. 140 kW
d. 275 kW

Answer 88

d

Question 89

Water flows over a waterfall that is 20 m high at the rate of 4.0 × 104 kg/s. If this water powers an
electric generator with a 40% efficiency, how many watts of electric power can be supplied?
a. 3.1 MW
b. 6.7 MW
c. 290 MW
d. 340 MW

Answer 89

a

Question 90

A 0.12-kg block is held in place against the spring by a 35-N horizontal external force. The external
force is removed, and the block is projected with a velocity when it separates from the
spring, as shown in the figure. The block descends a ramp and has a velocity at the bottom
of the ramp. The track is frictionless between points A and B. The block enters a rough section at B,
extending to E. The coefficient of kinetic friction between the block and the rough surface is 0.26. The
block moves on to D, where it stops. By how many centimeters was the spring initially compressed? a. 0.49 cm
b. 0.26 cm
c. 0.18 cm
d. 0.99 cm

Answer 90

a

Question 91

A 35-N bucket of water is lifted vertically 3.0 m and then returned to its original position. How much
work did gravity do on the bucket during this process?
a. 105 J
b. 90 J
c. 45 J
d. 0 J

Answer 91

d