Energy and Its Conservation
Practice Test
1.
In Figure 8-2, if the radius of the CD is 6.0 cm and the angular velocity is 5.0 rad/s, what is its angular displacement in 2.0 s?
a.
6.0×10
1
rad
b.
0.60 rad
c.
1.0×10
1
rad
d.
1.7 rad
Hint
2.
In Figure 8-3, why does applying a force as in the picture at the bottom left result in no effect?
a.
The force is applied at the axis of rotation.
b.
The force is applied perpendicular to the axis of rotation.
c.
The force is applied parallel to the lever arm.
d.
The force is applied perpendicular to the lever arm.
Hint
3.
A sled of mass 40.0 kg is pulled along flat, snow-covered ground. The static friction coefficient is 0.28, and the kinetic friction coefficient is 0.08. What force is needed to keep the sled moving at a constant velocity?
a.
3.2 N
b.
310 N
c.
31 N
d.
3900 N
Hint
4.
When the net external force on a closed system is zero, it is described as __________.
a.
an isolated system
b.
non-accelerating
c.
a normal system
d.
motionless
Hint
5.
If the boy in Figure 10-3 pushes on the car while it travels a horizontal distance of 1.1 m, how much work does he do?
a.
64 J
b.
120 J
c.
140 J
d.
58 J
Hint
6.
A large chunk of ice with mass 12.0 kg falls from a roof 6.00 m above the ground. Ignoring air resistance, what is the kinetic energy of the ice when it reaches the ground?
a.
-7.06×10
2
J
b.
7.06×10
3
J
c.
7.06×10
2
J
d.
-7.06×10
3
J
Hint
7.
The impulse is the product of the __________.
a.
angular momentum and torque
b.
mass and velocity of a moving object
c.
average force and the distance the object travels
d.
average force and the time interval over which it acts
Hint
8.
The __________ of a machine is defined as the ratio of output work to input work.
a.
reliability
b.
mechanical advantage
c.
IMA
d.
efficiency
Hint
9.
A large chunk of ice with mass 12.0 kg falls from a roof 6.00 m above the ground. Ignoring air resistance, what is the speed of the ice when it reaches the ground?
a.
12.1 m/s
b.
10.8 m/s
c.
12.5 m/s
d.
7.67 m/s
Hint
10.
A sailor pulls a boat 15.0 m along a dock using a rope that makes a 45.0° angle with the horizontal. How much work does the sailor do on the boat if he exerts a force of 185 N on the rope?
a.
2.78×10
3
J
b.
1.59×10
3
J
c.
1.96×10
3
J
d.
1.96×10
2
J
Hint
11.
An object is in __________ when the net force exerted on it is zero.
a.
rotational equilibrium
b.
equilibrium
c.
translational equilibrium
d.
static equilibrium
Hint
12.
When there is no relative motion between two surfaces, the force exerted by one surface on the other is called __________.
a.
the static friction force
b.
the kinetic force
c.
resistance
d.
kinetic friction
Hint
13.
A 75-kg rock climber first climbs 25 m to the top of a quarry, then descends 75 m from the top to the bottom of the quarry. If the initial height is the reference level, what is the potential energy of the system (climber plus Earth) at the top?
a.
-1.8×10
4
J
b.
3.7×10
4
J
c.
1.8×10
4
J
d.
-3.7×10
4
J
Hint
14.
Two campers dock a canoe. One camper has a mass of 100.0 kg and moves forward at 3.0 m/s as he leaves the canoe to step onto the dock. With what speed do the canoe and other camper move if their combined mass is 175.0 kg?
a.
1.7 m/s
b.
8.25 m/s
c.
5.3 m/s
d.
4.0 m/s
Hint
15.
The centripetal acceleration is given by:
a.
a
c
=
rω
2
b.
a
c
=
ω
2
/
r
c.
a
c
=
rω
d.
a
c
=
r
/
ω
Hint
16.
In Figure 8-3, why does applying a force as in the picture at the top left result in no effect?
a.
The force is applied parallel to the lever arm.
b.
The force is applied at the axis of rotation.
c.
The force is applied perpendicular to the lever arm.
d.
The force is applied perpendicular to the axis of rotation.
Hint
17.
A mass that rotates around its own axis is a(n) __________.
a.
rigid rotating object
b.
orbiter
c.
satellite
d.
projectile
Hint
18.
The force exerted by a machine is called the __________.
a.
mechanical advantage
b.
mechanical force
c.
effort force
d.
resistance force
Hint
19.
The __________ is the position at which gravitational potential energy is zero.
a.
reference level
b.
release point
c.
height
d.
initial position
Hint
20.
If an air bag such as the one shown in Figure 9-2 changes a 6.0×10
1
kg person's speed from 40.0 m/s to 0.0 m/s, what impulse must act on the person?
a.
1.5 kg m/s
b.
You cannot solve this problem without knowing the time it takes to stop the person.
c.
2400 kg m/s
d.
0.67 kg m/s
Hint
