Subject: Physics / General Physics
Question
Phy 111 Exam 2 (with all answers explained).
MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question.
1) If the net work done on an object is negative, then the object?s kinetic energy
A) increases.
B) remains the same.
C) is zero.
D) decreases.
E) cannot be determined without knowing the object mass.
1)
Three applied forces, F1 = 20.0 N, F2 = 40.0 N, and F3 = 10.0 N act on an object with a mass of 2.00 kg which can move
along an inclined plane as shown in the figure. Questions 2 and 3 refer to the instant when the object has moved 0.600
m along the surface of the inclined plane in the upward direction. Neglect friction and use g = 10.0 m/s2 .
2) What is the work done by force F2 as the object moves up the inclined plane?
A) 12.0 J
B) 16.0 J
C) 20.8 J
D) 24.0 J
3) What is the work done by the force F3 as the object moves up the inclined plane?
A) 20.8 J
B) 0 J
C) 16.0 J
D) 12.0 J
1
2)
E) 0 J
3)
E) 24.0 J
4) 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 one half as far.
B) It would have skidded 4 times farther.
C) It would have skidded 1.4 times farther.
D) It would have skidded twice as far.
E) It is impossible to tell from the information given.
4)
5) A lightweight object and a very heavy object are sliding with equal speeds along a level frictionless
surface. They both slide up the same frictionless hill. Which rises to a greater height?
A) The light object, because it has smaller kinetic energy.
B) They both slide to the same height.
C) The heavy object, because it has greater kinetic energy.
D) The lightweight object, because it weighs less.
E) The heavy object, because it weighs more.
5)
FIGURE 8-6
A roller coaster of mass 80.0 kg is moving with a speed of 20.0 m/s at position A as shown in the figure above. The vertical
height at position A above ground level is 200 m. Neglect friction and use g = 10.0 m/s2 .
6) What is the speed of the roller coaster at point B?
A) 66.3 m/s
B) 17.6 m/s
C) 46.9 m/s
D) 20.0 m/s
E) There is not enough information to solve this problem.
6)
7) An object of mass 4 kg is thrown vertically upwards from ground level with an initial speed of 20
m/s. Ignore friction and use g = 10 m/s2 . What is the kinetic energy of the object as it reaches its
7)
maximum height?
A) 800 J
B) 0 J
C) 400 J
D) 80 J
E) 200 J
8) In a collision between two unequal masses, how does the impulse imparted to the smaller mass by
the larger mass compare with the impulse imparted to the larger mass by the smaller one?
A) It is larger.
B) They are equal.
C) It is smaller.
D) The answer depends on the ratio of the masses.
E) The answer depends on how fast they are moving.
2
8)
9) A 0.140-kg baseball is dropped from rest from a height of 2.2 m above the ground. It rebounds to a
height of 1.6 m. What change in the ball?s momentum occurs when the ball hits the ground? (take g
= 9.80 m/s 2 ).
9)
A) 1.70 kg·m/s upwards
B) 0.117 kg·m/s upwards
C) 0.350 kg·m/s upwards
D) 0.350 kg·m/s downwards
E) 0.117 kg·m/s downwards
10) A 3.0-kg object moves to the right at 4.0 m/s. It collides head-on with a 6.0-kg object moving to
the left at 2.0 m/s. Which statement is correct?
A) The total momentum before the collision is 24 kg · m/s, and after the collision is 0 kg · m/s.
B) The total momentum both before and after the collision is zero.
C) The total momentum both before and after the collision is 24 kg · m/s.
D) The total momentum before the collision is 0 kg · m/s, and after the collision is 24 kg · m/s.
E) None of the above is true.
10)
11) A fan is turned off, and its angular speed decreases from 10.0 rad/s to 6.3 rad/s in 5.0 s. What is the
magnitude of the angular acceleration of the fan?
A) 0.86 rad/s2
11)
B) 1.16 rad/s2
C) 11.6 rad/s2
D) 0.74 rad/s2
E) 0.37 rad/s2
12) A child is riding a merry-go-round which completes one revolution every 8.36 s. The child is
standing 4.65 m from the center of the merry-go-round. What is the magnitude of the centripetal
acceleration of the child?
A) 0.0664 m/s2
12)
B) 6.84 m/s2
C) 0.696 m/s2
D) 3.94 m/s2
E) 2.63 m/s2
13) A Ferris wheel of radius 8.00 m rotates at a constant rate, completing one revolution in 30.0 s. What
is the apparent weight of a 60.0-kg passenger when she is at the top of the wheel? (take g = 9.80
m/s2 )
A) 567 N
B) 432 N
C) 325 N
D) 615 N
E) 589 N
14) Two equal forces are applied to a door at the doorknob. The first force is applied perpendicular to
the plane of the door; the second force is applied at 30° to the plane of the door. Which force exerts
the greater torque about the hinge line?
A) the second applied at an angle
B) both exert zero torques
C) the first applied perpendicular to the door
D) both exert equal non-zero torques
E) Additional information is needed.
3
13)
14)
15) An 82.0 kg-diver stands at the edge of a light 5.00-m diving board, which is supported by two
pillars 1.60 m apart, as shown in the figure above. Find the force exerted by pillar B on the board.
(take g = 9.80 m/s 2 )
15)
A) 1.71 kN downwards
B) 3.44 kN upwards
C) 2.51 kN downwards
D) 2.51 kN upwards
E) 1.71 kN upwards
16) A 60.0-kg man stands at one end of a 20.0-kg uniform 10.0-m long board. How far from the man
is the center of mass of the man-board system?
A) 5.00 m
B) 7.50 m
C) 9.00 m
D) 2.50 m
E) 1.25 m
16)
17) A merry-go-round spins freely when Janice moves quickly to the center along a radius of the
merry-go-round. It is true to say that (define the system as the merry-go-round + Janice)
A) the moment of inertia of the system decreases and the angular speed decreases.
B) the moment of inertia of the system decreases and the angular speed remains the same.
C) the moment of inertia of the system increases and the angular speed increases.
D) the moment of inertia of the system decreases and the angular speed increases.
E) the moment of inertia of the system increases and the angular speed decreases.
17)
18) Two objects attract each other gravitationally. If the distance between their centers is cut in half,
the gravitational force
A) is cut to one fourth.
B) is cut in half.
C) quadruples
D) remains the same
E) doubles.
18)
19) A satellite completes one full orbit around Earth. The work performed by Earth?s gravitational
force on the satellite is
A) negative most of the time.
B) always negative.
C) zero J.
D) always positive.
E) positive most of the time.
19)
20) The moons of Mars, Phobos (Fear) and Deimos (Terror), are very close to the planet compared to
Earth?s Moon. Their orbital radii are 9,378 km and 23,459 km respectively. What is the ratio of the
orbital speed, v, of Phobos to that of Deimos?
A) 1.582
B) 3.956
C) 0.3998
D) 0.2528
E) 2.858
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