Final Review
Concepts of Physics
Review Part II – Chapters 8-14
Work & Power
1) In physics, work is defined as
A) force times time.
B) force divided by time.
C). force times distance.
D) force divided by distance.
E) distance divided by time.
W=Fd
FΔt = mΔv
P=W/t
PE = mgh
KE = ½ m v2
2) If you lift two loads up one story, how much work do you do compared to lifting
just one load up one story?
A) Four times as much
B) Twice as much
C) The same amount
D) One half as much
E) One quarter as much
3) If you lift one load up two stories, how much work do you do compared to lifting
one load up only one story?
A) Four times as much
B) Twice as much
C) The same amount
D) One half as much
E) One quarter as much
4) How many joules of work are done on an object when a force of 10 N pushes it
5m?
A) 50 J
B) 10 J
C) 5 J
D) 2 J
E) 1 J
5) The unit of work is the
A) newton
B) watt
C) meter
D) joule
E) second
6) How much power is required to do 100 J of work on an object in 2 seconds?
A) 200 W
B) 100 W
C) 5OW
D) 2 W
E) OW
1
Final Review
7) The unit of power is the
A) newton.
D) joule.
Concepts of Physics
B) watt
E) second
C) meter
8) Potential energy is the energy an object has because of its
A) speed.
B) location.
C) size.
D) temperature
E) density.
9) The amount of potential energy possessed by an elevated object is equal to
A) the force needed to lift it.
B) the distance it is lifted.
C) the power used to lift it.
D) the work done in lifting it.
E) the value of the acceleration due to gravity.
10) How much work is done on a 50-N rock that you carry horizontally across a 10 m
room?
A) 500 J
B) 50 J
C) 10 J
D) 5 J
E) 0 J
11) How much work is done on a 50-N rock that you lift 10 m?
A) 500 J
D) 1 J
B) 50 J
E) O J
C) 10 J
Universal Gravitation
12) Why did Newton think there was a force acting on the moon?
A) Because the moon always keeps one side toward the earth
B) Because the moon moves in a curved path
C) Because there is no air on the moon
D) Because the moon is moving
E) All of the above
13) Newton had the insight to see that the
A) moon always keeps one side toward the earth.
B) moon orbits the earth.
C) moon is moving.
D) force on the moon has the same nature as the force on an apple
E) None of the above
2
Final Review
Concepts of Physics
14) Since the earth is attracted to the sun, why doesn’t it fall into the sun?
A) Because it has a large tangential velocity
B) Because there is an equal Force holding it away from the sun
C) Because it has too much mass to move toward the sun
D) Because it has too much inertia to move toward the sun
E) All of the above
15) The gravitational Force between two masses
A) is always an attraction.
B) depends on how large the masses are.
C) depends inversely on the square of the distances between the masses.
D) depends on a universal gravitational constant.
E) All of the above
16) Gravitational forces are the weakest forces found in nature because of this.
A) we cannot see the gravitational effect between a pencil and the earth.
B) there is no gravitational force between two 1-kg masses.
C) there is no movement between two 1-kg masses located near each other in
space.
D) we can see gravitational effects only when a large mass is involved.
E) gravitational forces between protons do not exist
17) Suppose the gravitational force between two masses is 10-N. If the distance
between the masses is cut in half, what is the force between the masses?
A) 40 N
B) 20 N
C) 10 N
D) 5 N
E) 2.S N
18) Suppose the gravitational force between two masses is 10-N. If the distance
between the masses is doubled, what is the force between the masses?
A) 40N
8) 20 N
C) 10 N
D) 5 N
E) 2.5 N
19) Suppose the gravitational force between two masses is 10-N. If the magnitude
of each mass doubles, what is the force between the masses?
A) 40 N
B) 20 N
C) 1O N
D) 5 N
E) 2.5 N
3
Final Review
Concepts of Physics
20) The component of an orbiting satellite’s velocity parallel to the earth’s surface
is called its tangential velocity. (T or F)
21) The force of attraction between two masses depends inversely on the square of
the distance between the masses. Any law that has this kind of dependence on
distance is called an inverse square law. (T or F)
Gravitational Effects
22) The value
A)
B)
C)
D)
E)
of the acceleration due to gravity, g.
depends on the radius of the earth.
depends on the mass of the earth
depends on the universal gravitational constant. G.
is different on different planets.
All of the above
23) if the earth had twice its present mass, but the same radius, what would be
the value of g?
A) 39.2 m/s/s
B) 19.6 m/s/s
C) 9.8 m/s/s
D) 4.9 m/s/s
E) 0 m/s/s
24) If the radius of the earth were one half what it is now, and the mass were
the same, what would be the value of g?
A) 39.2 m/s/s
B) 19.6 m/s/s
C) 9.8m/s/s
D) 4.9 m/s/s
E) 0 m/s/s
25) We can tell if a gravitational force exists in a region of space if
A) we let go of a ball and it starts to move.
B) we disturb a pendulum and it starts swinging.
C) a force exists on a mass placed there
D) we can weigh ourselves.
E) All of the above
26) Gravitational field lines show the
A) direction a mass would be accelerated.
B) direction of the field at each point.
C) direction of the force on any mass.
D) strength of the Field.
E) All of the above
Fg = G m1 m2 / d2
g = G ME / r2
G = 6.67 x 10-11 Nm2/kg2
mearth = 5.98 x 1024 kg
rearth = 6.38 x 106m 4
Final Review
Concepts of Physics
27) The gravitational field strength at the center of the earth is
A) large.
B) the same as on the surface.
C) smaller than on the surface but still larger than zero.
D) zero.
28) If you were to weigh yourself in an elevator that is accelerating upward.
compared to your ordinary weight you would weigh
A) more.
B) the same.
C) less, but more than zero.
D) zero.
29) A straight line around which rotation takes place is called an axis. (T or F)
30) The rotational speed of a wheel is the number of rotations it makes in a 10second interval. (T or F)
31) Any force that causes an object to move in a circular path is called a centripetal
force. (T or F)
32) Centrifugal forces are forces we invent to explain the effects of inertia in a
rotating reference frame. (T or F)
33) It is possible to rotate a very large cylindrical space habitat around its
central axis at just the right speed so people living inside the cylinder will
experience a force that feels like gravity. (T or F)
34) The only reason riders on a rotating platform in a carnival ride don’t fall out is
because they are strapped in. (T or F)
35) A bug on a turning record will make more turns per minute if it walks
toward the center of the record. (T or F)
36) When you whirl a can on the end of a string, the centripetal force on the
can is actually the pull of the string on the can. (T or F)
37) Ladybugs on the inside of a spinning bicycle tire may experience a force that
feels like gravity to them. (T or F)
5
Final Review
Concepts of Physics
Rotational Mechanics
38) Torque is defined as
A) mass times velocity.
B) force times time.
C) force times lever arm
D) mass times acceleration.
E) momentum times radius.
39) Suppose you try loosening a nut with a wrench, and the nut doesn’t give at
all. To loosen the nut you could
A) extend the lever-arm.
B) be sure to exert force perpendicular to the lever arm.
C) exert a larger force.
D) have a friend help you pull on the wrench.
E) All of the above
40) Why are door knobs placed at the edge of a door rather than in the center?
A) because its closer to the edge of the doorway.
B) To help give more momentum to the door
C) Because it looks better there
D) To increase the force on the door
E) To increase the lever- arm
41) A meter stick is balanced at the 50-cm mark. You tie a 20-N weight at the
30-cm mark. Where should a 30-N weight be placed so the meter stick will
again be balanced?
A) 20 cm mark
B) 30 cm mark
C) 50 cm mark
D) 70 cm mark
E) 80 cm mark
42) lf you were to weigh yourself in an elevator that is in free fall, compared to your
ordinary weight, you would weigh
A) more.
B) the same
C) less, but more than zero.
D) zero
43) To be truly weightless you would have to be
A) in free fall
B) in a satellite orbiting the earth.
C) on the moon.
D) far away from any planet or star.
E) All of the above
6
Final Review
Concepts of Physics
Circular Motion
44) Which has greater linear speed a horse near the outside rail of a merry-goround or a horse near the inside rail?
A) The outside horse
B) The inside horse
C) Neither—they both have the same linear speed.
45) Which has greater angular speed, a horse near the outside rail of a merry-goround or a horse near the inside rail?
A) The outside horse
B) The inside horse
C) Neither—they both have the same angular speed.
46) Which of the following is NOT a unit of rotational speed?
A) Revolutions per second
B) Rotations per second
C) Revolutions per minute
D) Meters per second
E) Rotations per minute
47) What is the direction of the force that act on clothes in the spin cycle of a
washing machine?
A) Outward
B) Inward
C) Up
D) Down
48) A tin can whirled on the end of a string moves in a circle because
A) once the can starts moving, that is its natural tendency.
B) the can continually pulls on the string.
C) there is a force on the can pulling it outward.
D) there is an inward force acting on the can.
E) All of the above
49) If you whirl a tin can on the end of a string and the string suddenly breaks.
the can will
A)
fly directly away from you.
B)
fly directly toward you.
C)
fly off, tangent to its circular path.
D)
spiral away from your hand.
E)
spiral in toward your hand.
50) lf a football is kicked so the force on the ball is through its center of gravity,
the ball will
A) tumble end over end in the air
B) spin about its axis in the air
C) move without any tumbling or spinning.
D) not even get into the air.
E) deflate
7
Final Review
Concepts of Physics
51) The resistance of an object to changes in its rotational state of motion is
rotational
A) momentum.
B) inertia.
C) torque
D) acceleration.
E) velocity
called
ω = 2(rad) / Τ
Fc = mυ2 / r
υ = ωr
ac = v2 /r
52) Which has more rotational inertia, a bicycle wheel or a solid disk of the same
mass and diameter?
A) The wheel.
B) The disk
C) They both have the same rotational inertia.
53) Which has more rotational inertia, a girl running with her legs bent or the same
girl running with her legs straight?
A) With bent legs
B) With straight legs
C) Both have the same rotational inertia
54) Which objects roll down an incline with the greatest acceleration?
A) Objects with large rotational inertia
B) Objects with small rotational inertia
C) Acceleration is independent of rotational inertia in this case.
55) Any solid cylinder will roll down an incline with greater acceleration than any
hollow cylinder if
A) the mass of the solid cylinder is large.
B) the diameter of the solid cylinder is small.
C) the diameter of the solid cylinder is Large.
D) the mass of the solid cylinder is small
E) The solid cylinder always wins regardless of masses or diameters.
56) A person’s rotational inertia is least about
A) the person’s longitudinal axis.
B) the person’s transverse axis.
C) the person’s median axis.
D) an axis through the persons hands.
E) an axis through the person’s feet.
57) When a gymnast goes from an extended position to a tucked position, she
A) increases her rotational inertia.
B) decreases her rotational inertia.
8