6. The force applied to the cart in Question 5 by spring scale F1 is still 10.5 N. The cart now moves toward the right with a constant velocity. What are the magnitude and direction of the frictional force? Show your calculations and explain your reasoning.
7. The force applied to the cart in Question 5 by spring scale F1 is still 10.5 N. The cart now moves toward the right with an acceleration also toward the right of 1.75 m/s2. What are the magnitude and direction of the frictional force? Show your calculations and explain.
8. The force applied to the cart by spring scale F1 is 10.5 N. The cart now moves toward the right with a constant velocity. The frictional force has the same magnitude as in Question 7. What does spring scale F2 read? Show your calculations and explain.
In Questions 6 – 8, friction may not be ignored.

The distance between the front and rear wheels of a 2280 kg car is 3.15 m. The car’s center of gravity lies in the middle of the car, 1.05 m behind the front wheels. When the car is at rest, what is the ratio of the force exerted by the ground on the front wheels to that exerted on the rear wheels?
Select one:
a. 3.0
b. 0.50
c. 0.33
d. 2.0
Question 12
Question text
A pendulum bob has mass of 0.750 kg and is on a pendulum arm of length 1.00 m. The pendulum is pulled back so that the arm makes an angle of 60.0° from the vertical and is then released. Which of the following is the speed of the mass when it reaches its lowest point?
Select one:
a. 3.68 m/s
b. 3.13 m/s
c. 4.43 m/s
d. 4.12 m/s
Question 13
Question text
A 1,450 kg car moves with a speed of 25.0 m / s when it collides with a stationary car having a mass of 1,550 kg. The two vehicles lock bumpers on impact. The two cars then collide with a stationary third car of mass 1,250 kg. During this second impact, the third vehicle becomes attached to the second but the first car is breaks free and moves at 0.125 m / s in the opposite direction. Which of the following is the final velocity of the second and third cars after the final collision?
Select one:
a. 12.88 m / s
b. 12.14 m / s
c. 14.42 m / s
d. 13.01 m / s
Question 14
Question text
Select one:
a. 50.0 N
b. 42.3 N
c. 38.3 N
d. 32.1 N
Question 15
Question text
An empty freight train car of mass 10,000 kg is rolling along a level section of track at 2.00 m / s. It collides with a loaded car of weight 1.96 × 105 N, which is at rest. The cars couple upon collision. Which of the following is the speed of the train after the collision?
Select one:
a. 1.02 m / s
b. 0.667 m / s
c. 2.00 m / s
d. 3.02 m / s
Question 16
Question text
Which of the following is not a unit of power?
Select one:
a. Joule / second
b. Watt / second
c. ft ⋅ lb / s
d. horsepower
Question 17
Question text
A 0.500 kg steel ball is dropped from a height of 4.00 m onto a horizontal steel slab. The collision appears elastic in that the ball rebounds to its original height. If the collision lasts for 2.00 × 10−3 s, which of the following is the impulse imparted to the ball and the average force applied to the ball during the collision?
Select one:
a. I = 8.49 kg•m / s
F = 4.25 × 103 N
b. I = 8.85 kg•m / s
F = 4.43 × 103 N
c. I = 8.00 kg•m / s
F = 4.00 × 103 N
d. I = 8.86 kg•m / s
F = 2.22 × 103 N
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Question 18
Question text
Why are gyroscopes useful?
Select one:
a. They do not flip over so you always know which way is up.
b. They always precess in the same direction.
c. They respond differently depending on their position on the Earth.
d. They respond differently at different altitudes.
Question 19
Question text
A spaceship is in space and currently at rest. The directive is given to accelerate from rest to a speed of 2.90 &times 103 m / s. If the fuel budgeted for this action is 400 kg, which of the following is velocity of the exhaust gas required if the ship mass is 7.38 &times 103 kg?
Select one:
a. 955 [m / s]
b. −955 [m / s]
c. –5.5 × 104 [m / s]
d. −1.01 × 103 [m / s]
Question 20
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True or false?
Clockwise rotations are always positive.
Select one:
a. false
b. true
Question 21
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A roller coaster has 8 cars, each of mass of 95.0 kg. The first hill of the ride is 24.8 m above the ground. Which of the following is the gravitational potential energy of the train once the last car had reached the top of the hill?
Select one:
a. 2.31×104 J
b. 1.85×105 J
c. -2.31×104 J
d. -1.85×105 J
Question 22
Question text
A hanging mass m is connected to another mass M free to slide horizontally over a frictionless surface, as shown. The pulley has a radius R and a moment of inertia I. If the system is released from rest, what is its angular momentum about the center of the pulley 5 seconds later?
Select one:
a. mg
b. 5mg
c. mgR
d. 5mgR
Question 23
Question text
A centrifuge is a device that spins small containers of substances at high speeds. A certain centrifuge can be modeled by four masses connected by massless rods to a rotating pivot, as shown.
Suppose that the masses are each 0.035 kg and that the rods are 8.0 cm long. How much energy does it take to accelerate the centrifuge up to 8,000 rotations per minute (from rest)?
Select one:
a. 310 J
b. 3800 J
c. 3900 J
d. 29,000 J
Question 24
Question text
The work done to accelerate a car from 0 m / s to 40 m / s is _____ times greater than the work done to accelerate it from 0 m / s to 20 m / s?
Select one:
a. two
b. three
c. four
d. eight
Question 25
Question text
In a game of marbles, a 60 g marble is rolling at 8.00 cm / s when it collides with a stationary marble. the 60 g marble takes off at a 27° angle at a reduced speed of 4.89 cm / s. The second marble moves at a rate of 3.21 cm / s at a 31.7° angle. Which of the following is the mass of the second marble?
Select one:
a. 58.1 kg
b. 0.0581 kg
c. 0.0800 kg
d. 80.0 kg