Section 11.2
Conservation of Energy
Practice Test
1.
In Figure 11-12, if cart D were given an initial velocity of 1 m/s to the left, what would the final velocities of each cart be?
a.
cart C, 0 m/s; cart D, 2 m/s to the right
b.
cart C, 0 m/s; cart D, 0 m/s
c.
cart C, 2 m/s to the left; cart D, 1 m/s to the left
d.
cart C, 1 m/s to the left; cart D, 1 m/s to the right
Hint
2.
A collision in which kinetic energy decreases is called a(n) __________.
a.
inelastic collision
b.
mechanical collision
c.
energy conservation
d.
elastic collision
Hint
3.
If no other forms of energy besides kinetic and gravitational potential energy are present, then mechanical energy is represented by the equation __________.
a.
PE
g
=
E
+
KE
b.
PE
g
=
mgh
c.
M
E
= 1/2 (
KE
)(
PE
g
)
2
d.
E
=
KE
+
PE
g
Hint
4.
The sum of the kinetic and gravitational potential energies of a system is called __________.
a.
conserved energy
b.
reference energy
c.
mechanical energy
d.
momentum
Hint
5.
The law of conservation of energy states that __________.
a.
the total amount of energy in any system is the sum of its kinetic and gravitational potential energies
b.
in a closed, isolated system, the total amount of energy is constant
c.
if a system is isolated from external forces, then the total amount of energy is constant
d.
the total amount of energy in any system is its mechanical energy
Hint
6.
In Figure 11-5, estimate the vertical velocity of an orange when it hits the juggler's left hand.
a.
0.45 m/s
b.
2 m/s
c.
4.5 m/s
d.
20 m/s
Hint
7.
A 4.5-kg rock loses 375 J of potential energy while falling to the ground. What is the rock's speed just before it strikes the ground?
a.
18 m/s
b.
9.1 m/s
c.
20 m/s
d.
13 m/s
Hint
8.
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
3
J
b.
7.06×10
2
J
c.
-7.06×10
2
J
d.
7.06×10
3
J
Hint
9.
In an accident on a slippery road, a car with mass 800.0 kg, moving at 12.0 m/s, smashes into the rear end of a car with mass 1250 kg moving at 8.0 m/s in the same direction. How much kinetic energy was lost in the collision if the wrecked cars lock together?
a.
3.9×10
3
J
b.
4.1×10
4
J
c.
3.9×10
4
J
d.
6.1×10
4
J
Hint
10.
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.
10.8 m/s
b.
7.67 m/s
c.
12.1 m/s
d.
12.5 m/s
Hint
11.
A bike rider approaches a hill at a speed of 3.5 m/s. The mass of the bike and rider together is 77 kg. The rider coasts up the hill. Assuming that there is no friction, at what height will the bike come to rest?
a.
1.6 m
b.
3.7 m
c.
4.1 m
d.
0.62 m
Hint
12.
In Figure 11-13, case 3, if
v
i
were doubled, how would the magnitude of the final velocity be affected?
a.
It would be doubled.
b.
It would be halved.
c.
It wouldn't change.
d.
It would be quadrupled.
Hint
13.
If the mass of the ball rolling down the ramp in Figure 11-10 were doubled, how would its speed at the bottom of the ramp be affected?
a.
It would be halved.
b.
It would be quadrupled.
c.
It wouldn't change.
d.
It would be doubled.
Hint
14.
A bike rider approaches a hill at a speed of 3.5 m/s. The mass of the bike and rider together is 77 kg. What is the initial kinetic energy of the system?
a.
4.7×10
2
J
b.
1.2×10
3
J
c.
2.6×10
3
J
d.
3.1×10
3
J
Hint
