Sample Exam II
Put your scantron inside your exam when you turn them in.
Multiple Choice: 2 points each. Choose the BEST Answer(s).
Let me know it you have any erasures on your scantron!
1. An object cannot have both potential energy and kinetic energy
at the same time.
A) True B) False
2. A ball weighing 4N rolls 5m along a level (i.e. horizontal) table with
a constant speed. The work that gravity
does on the ball is
A) 20J B) 1.2J C) 0.8J D)
0
3. A light bulb uses 1000J of electrical energy to produce 50J of
visible light. Its efficiency at
converting electrical energy into light is
A) 200% B) 20% C)
5% D) 0.05%
4. I cut a
piece of lead in half and throw one half away.
The density of the remaining half
A) increases by a factor of two.
B) decreases by a factor of two.
C) stays the same.
5. A box weighs 20N at the surface of the earth. If the mass of the earth were doubled,
keeping the radius the same, the box would weigh
A) 5N B)
10N C) 20N
D) 40N E) 80N
6. A 20N weight will stretch a spring 0.15m. Another weight stretches the same spring
0.3m. What is the weight of this second
weight?
A) 10N B) 20N C)
40N
7. 
If the gravitational force
the sun is exerting on the earth was somehow removed, the earth would
A) move in a straight line in the
direction it was going
B) fall into the sun
C) move directly away from the sun.
D) continue its circular motion about the sun
8. I hold a 20N weight at a fixed position 1m above the
ground for 10s. The rate at which I’m
doing work on the weight, i.e. the power, is
A) 0 B) 2W C)
200W D) 0.5W
9. A 2kg
mass has a speed of 3m/s. Its kinetic
energy is
A) 6J B) 3J C) 18J D) 9J
10. I have a block of foam of density 200kg/m3 and volume
1m3. If I compress it so its
volume is decreased to 0.5m3.
Its density will become
A) 400kg/m3 B) 250kg/m3 C)
100kg/m3 D) 0.0025kg/m3
11. I throw a 1kg ball upward with an initial
speed of 20m/s. As it rises
A) its kinetic energy decreases and it gravitational potential
energy decreases
B) its kinetic energy decreases and it gravitational potential
energy increases
C) its kinetic energy increases and it gravitational potential
energy decreases
D) its kinetic energy increases and it gravitational potential
energy increases
12. A block is in the form of a
cube of edge 0.1m. Its volume is
A) 0.1m3 B) 0.3 m3 C) 0.001 m3 D) 0.01
m3
13. Cobalt has a density of 9,000 kg/m3
and tungsten’s is 19,000 kg/m3. If I have
0.1m3 of Cobalt and 0.1m3 of tungsten, the tungsten’s
mass will be
A) greater than the
cobalt’s mass
B) the same as the
cobalt’s mass
C) less than the cobalt’s mass
14. I
drop a ball off a cliff. As it falls
A) Gravity does negative
work on it.
B) Gravity does positive
work on it.
C)
Gravity does no work on it.
15. I exerted a force of 50N on a block of mass 8kg as it moved
3m. The force was parallel to the
motion. The work I did on the block was
A) 400J B) 150J C) 24J D)
16.7J E) 240J
16. As two masses move apart,
and the distance between them doubles, the gravitational force they exert on
each other
A) increases by a
factor of 2 B) decreases
by a factor of 2
C) increases by a
factor of 4 D) decreases
by a factor of 4
17. A 10kg mass initially has a kinetic energy
of 20J. If its kinetic energy increases
to 25J,
A) Its speed
will decrease
B) Its speed
will increase
C) Its speed
will remain the same.
18. If the earth’s tangential
velocity about the sun were somehow removed, the earth would
A) move in a straight
line in the direction it was going when the force was removed
B) move directly away
from the sun
C) fall into the sun.
D) continue its
circular motion about the sun
19. A 200kg mass has a density of 2,000 kg/m3. Its volume is
A) 10m3 B) 1m3 C)
0.1m3 D) 400,000m3
20. The gravitational force between two masses
is
A) always repulsive
B) always attractive
C) repulsive when they are
close together and attractive when they are far apart.
21. One atom has 18 protons and
18 neutrons in its nucleus. Another has
20 neutrons and 18 protons in its nucleus.
They
A) are different
elements
B) are different
isotopes of the same element
C) have the same mass
number
22. A 2kg block is 6m above the ground and a 4kg block is 3m above
the ground. Which block has the most
gravitational potential energy relative to the ground?
A) The
2kg B) the 4kg C) They have
the same potential energy
23. Which of the following is not found in the
nucleus of an atom?
A) protons B) electrons C) neutrons
24. A light bulb uses 100W as it operates for 10s. The energy it used in those 10s is
A) 10J B) 100J C)
1000J D) 10,000J
25. Most of the volume of an atom is due to which
of the following
A) the neutrons
B) the electron cloud
C) the protons
D) the nucleus
Short Answer: 6
points each. SHOW ANY WORK! (Do All 5)
1. The weights shown at the right are balanced (in
equilibrium). The 20N weight is 5m to
the left of the fulcrum and the unknown weight is 2m to the right. What is the weight of the unknown mass? (Assume you can neglect the weight of the
board, or that its center of gravity is over the fulcrum.)
2. Radon 222 has 86 protons in its nucleus. It is produced when atom X undergoes alpha
decay. That is, atom X emits an He-4 nucleus (2 protons and 2 neutrons) and becomes Radon
222.
a) What is the atomic number of atom X before it undergoes alpha
decay and becomes Radon 222?
b) What is
the mass number of the atom X?
3. A 4kg block is moving with a
speed of 7m/s and a 8kg block has a speed of
5m/s. Which has the
greater kinetic energy. (You MUST
SHOW WHY your answer is correct.)
4. An
astronaut in the space station orbiting 250km above the earth’s surface appears
to be weightless when weighed on a scale.
Why? Does the earth exert an appreciable force on
her? (Explain!)
5. A car of mass 1500kg is moving on a level road with a speed of
10m/s. How much work would I have to do
on it to stop it?
Formulas
Change in Position = Final Position – Initial
Position, 1N = 1kgm/s2 1J = 1kgm2/s2, 1Pa = 1N/m2
