MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question.
1) The work done by the centripetal force on an object with a mass of 1 kg moving with a constant velocity of 4 m/s into a circular path of radius 0.6 m for one full cycle is
A) 100.7 J B) 3.8 J C) 0 J D) 80 J
Answer: C
2) 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 = 1/2 Kc
Answer: A
Figure 7-4
3) An object is under the influence of a force as represented by the force vs. position graph in Figure 7-4. What is the work done as the object moves from 6 m to 12 m?
A) 20 J B) 30 J C) 0 J D) 40 J
Answer: B
4) A car accelerates from rest to a speed of 20.0 m/s in 6.00 seconds. If the car weighs 16,000 N, what average power must the motor produce to cause this acceleration?
A) 128 kW B) 15.0 kW C) 54 .4 kW D) 219 kW
Answer: C
A mass of 1.0 kg is pushed against a spring with a spring constant of 25 N/m. As a result, the spring is compressed by 20 cm. The mass is then released.
5) What is the amount of work required to compress the spring?
A) 5.0 J
B) 0.20 J
C) 0.50 J
D) 10 J
Answer: C
6) An object of mass m is held at a vertical height h from ground level. It is then released and falls under the influence of gravity. Which of the following statements is true in this situation? (Neglect air resistance.)
A) The total energy of the object is decreasing.
B) The kinetic energy of the object is decreasing.
C) The total energy of the object is increasing.
D) The potential energy of the object is decreasing and the kinetic energy is increasing.
Answer: D
Figure 8-7
An object with a mass of 10.0 kg is at rest at the top of a frictionless inclined plane of height 8.00 m and an angle of inclination 30.0e with the horizontal. The object is released from this position and it stops at a distance d from the bottom of the inclined plane along a horizontal surface, as shown in Figure 8-7. The coefficient of kinetic friction for the horizontal surface is 0.400 and g = 10.0 m/ s to power of (exponent).
7) Refer to Figure 8-7. What is the kinetic energy of the object at the bottom of the inclined plane?
A) 400 J
B) 500 J
C) 700 J
D) 800 J
Answer: D
Figure 8-10
2-kg mass is moving along the x axis. The potential energy curve as a function of position is shown in Figure 8-10. The system is conservative. There is no friction.
8) Refer to Figure 8-10. If the object is at rest at the origin, what will be its speed at 9.0 m along the +x-axis?
A) 1.5 m/s
B) 2.5 m/s
C) 3.5 m/s
D) 4.5 m/s
Answer: C
9) A golf club exerts an average force of 1000 N on a 0.045-kg golf ball which is initially at rest. The club is in contact with the ball for 1.8 ms. What is the speed of the golf ball as it leaves the tee?
A) 35 m/s
B) 40 m/s
C) 45 m/s
D) 50 m/s
Answer: B
10) 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) It is smaller.
C) They are equal.
D) The answer depends on how fast they are moving.
Answer: C
11) An elastic collision of two objects is characterized by the following.
A) Total momentum of the system is conserved.
B) Total kinetic energy of the system remains constant.
C) Both A and B are true.
D) Neither A nor B are true.
Answer: C
12) A uniform piece of wire, 20 cm long, is bent in a right angle in the center to give it an L-shape. How far from the bend is the center of mass of the bent wire?
A) 2.5 cm
B) 3.5 cm
C) 5.0 cm
D) 7.1 cm
Answer: B
13) How long does it take a wheel that is rotating at 33.3 rpm to speed up to 78.0 rpm if it has an angular acceleration of 2.15 rad/ s to power of (exponent)?
A) 20.8 s
B) 10.4 s
C) 2.18 s
D) 5.20 s
Answer: C
14) A Ferris wheel with a radius of 12.0 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?
A) 589 N
B) 557 N
C) 615 N
D) 325 N
Answer: B
15) A dumbbell-shaped object is composed by two equal masses, m, connected by a rod of negligible mass and length r. If I1 is the moment of inertia of this object with respect to an axis passing through the center of the rod and perpendicular to it and I2 is the moment of inertia with respect to an axis passing through one of the masses we can say that
A) I1 = I2
B) I1 > I2
C) I1 < I2
D) There is no way to compare I1 and I2.
Answer: C
16) A solid disk, a hoop, and a solid sphere are released at the same time at the top of an inclined plane. They all roll without slipping. In what order do they reach the bottom?
A) disk, hoop, sphere
B) sphere, disk, hoop
C) hoop, sphere, disk
D) hoop, disk, sphere
Answer: B
17) The rotating systems shown in the figure differ only in that the two identical movable masses are positioned a distance r from the axis of rotation (left), or a distance r/2 from the axis of rotation (right). If you release the hanging blocks simultaneously from rest,
A) the block at left lands first.
B) the block at right lands first.
C) both blocks land at the same time.
D) it is impossible to tell which block reaches the bottom first.
Answer: B
18) A 3.00-m-long ladder, weighing 200 N, rests against a smooth vertical wall with its base on a horizontal rough floor, a distance of 1.20 m away from the wall. If the center of mass of the ladder is 1.40 m from its base, what frictional force must the floor exert on the base of the ladder in order for the ladder to be in static equilibrium?
A) 93.3 N
B) 130 N
C) 40.7 N
D) 102 N
Answer: C
19) A puck moves on a horizontal air table. It is attached to a string that passes through a hole in the center of the table. As the puck rotates about the hole, the string is pulled downward very slowly and shortens the radius of rotation, so the puck gradually spirals in towards the center. By what factor will the puck's angular speed have changed when the string's length has decreased by 1/2?
A) 2
B) 4
C) sqrt(2)
D) 1
Answer: B
Figure 11-6
20) The L-shaped object shown in Figure 11-6 consists of the masses connected by light rods. How much work must be done to accelerate the object from rest to an angular speed of 3.25 rad/s about the y-axis?
A) 374 J
B) 173 J
C) 42.2 J
D) 27.4 J
Answer: B
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