PHYS 1400:
P H Y S I C A L S C I E N C E F O R G E N E R A L E D U C AT I O N
SPRING
2017
E x a m 0 2 : C h apte r s 03–05
1.
2.
In the context of physics, work is
A) that thing you do every day to earn a paycheck.
B) a constant quantity representing the mass of an object.
C) a vector quantity representing an object’s state of
motion.
D) a scalar quantity representing the process by
which an object’s state of motion can be changed.
A student pushes a fully loaded grocery cart, applying a
horizontal force of 90 lb (400 N) to push the 80 lb (355N) cart
a distance of 50ft (15m) down the store aisle. How much
work has the student done?
A)
B)
W = 23.7 J
W = 26.7 J
C)
D)
W = 755 J
W = 5,325 J
E)
F)
W = 6,000 J
W = 11,325J
3.
How much work has been done by the force of gravity on
the grocery cart?
A) W = (355 N) × (15 m) = 5,325 J
B) W = (400 N) × (15 m) = 6,000 J
C) W = (400 N – 355 N) × (15 m) = 675 J
D) W = (355 N + 400 N) × (15 m) = 11,325 J
E) Zero! Gravity is perpendicular to the motion!
4.
An object is in motion when a force is applied to it. The force
does negative work on the object. What does this mean?
Doing negative work on an object
A) will slow it down.
B) will speed it up.
C) will cause no change to its motion.
D) will change its direction of motion (i.e., from +x to –y).
5.
How much power is developed when Butch (m=75kg) runs
up a staircase (h=5m) in a time t=7s?
A)
B)
6.
7.
8.
P = 0W
P = 53.5W
C)
D)
P = 75W
P = 105W
E)
F)
P = 525W
P = 1029W
At 80kg, Sundance is more massive than Butch. If he
actually develops less power running the same 5 m
staircase, he must have run them in
A) less time.
B) more time.
C) exactly the same amount of time.
D) Trick question! More mass, more power. Always.
Rumor has it that the 2018 Dodge Challenger Demon can
develop an incredible 815 hp! What does this mean? What is
horsepower?
A) The unit is figurative; when cars began to replace
horses in the early 1900s, people used to joke about a
car taking the place of 2 horses.
B) The unit is literal, and based on actual estimates
of how much work a typical horse could do:
lifting a 220lb load through 100 feet per minute
over a 4 hour shift.
In the context of physics, energy is
A) a constant: all objects contain equal energy.
B) a process: an object can do/perform energy.
C) a property: an object can have/possess energy.
D) a mystery. Physicists have no idea how energy works.
9.
Which of the following is not a form of potential energy?
A) Gravitational.
D) Spring (or elastic).
B) Electrical.
E) All of these are
C) Magnetic.
examples of PE!
10. True or false: An object at rest may possess potential
energy.
11. True or false: An object may have either positive or negative
potential energy.
12. A simple recurve bow has a 27lb draw, which means it
requires 27lb of force to fully extend the bowstring.
True or false: A partially drawn bowstring will have the same
potential energy as a fully drawn string.
13. Two tennis balls are held above
the ground as shown on the
right. You want the calculate
the potential energy of each,
PEA and PEB. If you choose the
reference level shown (h = 0),
what can you say about the
potential energy of each ball?
A) Nothing; if the balls are at
h=0
rest, the PE of each is
exactly zero.
B) Because the balls have the
same mass, the potential
energy must be the same:
PEA = PEB.
C) Because both balls are
above the floor, the
potential energy of each
ball is positive.
D) If h = 0 is between the
two balls, then PEB is
positive, and PEA is
negative.
E) If h = 0 is between the two balls, then PEA is positive,
and PEB is negative.
14. When you release Ball B from rest, it will fall to the floor. As
the ball falls, what happens to its energy?
A) Nothing. KE and PE both remain constant.
B) Its KE decreases as its PE increases.
C) Its KE increases while its PE decreases.
D) Both KE and PE decrease.
E) KE and PE both increase.
15. True or false: Kinetic energy can be positive or negative. An
object with positive mass has positive KE, and an object with
negative mass has negative KE.
16. Calculate the kinetic
energy of a 150 lb (m = 68
kg) cyclist moving at 19
mph (v = 8.5 m/s).
Answer numerically
(do not include units).
P H Y S 1 4 0 0
17. How many forms of energy are there?
A) Exactly zero. Energy does not exist.
B) Exactly one: kinetic energy.
C) Exactly two: energy may be kinetic or potential.
D) Many. KE and PE are two examples, but there
exist other forms of energy as well.
18. True or false: If you transform chemical energy (breakfast)
into mechanical energy (walking across campus), you will
also generate waste heat.
19. True or false: Some energy transformations are possible
(like potential to kinetic), but other transformations are not
possible (like mechanical to electrical).
20. In physics, what do we mean by conservation of energy?
A) Energy is continually created, but without careful
conservation, it will be easily destroyed.
B) Energy cannot be created, so unless it is carefully
conserved, it will be destroyed, leaving nothing.
C) Energy cannot be created or destroyed; it can only
be transferred from one object to another, or
transformed from one type of energy to another.
D) Energy cannot be created or destroyed. It cannot be
transferred from one object to another, and it definitely
cannot change form (like from electrical to mechanical).
21. Distinguish between an atom and a molecule.
A) An atom is a single particle (like hydrogen). When two
or more atoms are joined, it becomes a molecule (like
water = H2O = 2 hydrogen atoms + 1 oxygen atom).
B) An atom is the smallest particle of a solid, while a
molecule is the smallest particle of a liquid or gas.
C) An atom is a group of ten particles bonded together.
Molecules are larger, and consist of 1 million particles
bonded into a single unit.
D) Technically, answer A is correct. However, for
the purposes of Kinetic Theory, we can refer to
either atoms or molecules as “molecules.”
22. Which of the following is an example of cohesion?
A) Using masking tape to seal a moving box.
B) Using a weird rubbery material to suspend a car upside
down from the ceiling.
C) Observing dewdrops on the grass in the morning.
D) Using a magnet to display a photo on the fridge.
E) All of these, except answer C!
23. If both liquids and gases are fluids, what is the difference
between them?
A) Liquids are made of molecules, while gases are made
up of atoms.
B) A liquid has fixed volume, but variable shape.
Gases have both variable volume and shape.
C) A liquid has almost zero cohesive bonding between
molecules, while gases have strong cohesive bonds.
D) All of these answers are accurate!
24. True or false: The molecules of a solid material are
stationary, and cannot move at all.
EXAM 02
SPRING
2017
25. Which of the following is not an example of molecular
motion by diffusion?
A) You light a candle and the wax melts into a liquid
pool surrounding the wick.
B) A drop of food coloring gradually turns an entire glass of
water red.
C) You can smell dinner cooking in the kitchen even if you
are down the hall and in your bedroom.
D) Boiling water poured over herb leaves in a mug results
in a delicious cup of tea.
26. Briefly summarize the idea of Kinetic Molecular Theory.
A) Because only fluids flow, liquids and gases have kinetic
energy. Solids cannot have kinetic energy.
B) All molecules are moving, always. Solids are the
lowest energy phase, and gases have the highest
energy.
C) Individual molecules cannot have kinetic energy, but
any object made of the molecules will have KE.
D) When one molecule collides with another, it gives its KE
to that molecule and stops moving forever.
27. Temperature is defined as the average
A) heat of an object.
B) chemical potential energy per molecule of a substance.
C) gravitational PE per molecule of a substance.
D) internal kinetic energy per molecule of a
substance.
E) energy transferred from one substance to another
because of a temperature difference.
28. Explain thermal expansion. When you increase the
temperature of a substance, the molecules move
A) faster, get farther apart, and occupy more space.
B) faster, get closer together, and occupy a smaller volume.
C) more slowly, get closer together, and occupy less space.
D) more slowly, drift apart, occupy a greater volume.
29. Consider a cube of metal (like we used in lab) with
dimensions length L, width W, and height H. When you put
it in boiling water and its temperature increases, it expands
A) in zero dimensions, or not at all. The cube remains
exactly the same size: L, W, and H remain unchanged.
B) in one dimension only: L gets bigger, while W and H
remain constant.
C) in two dimensions: L and W increase, while H remains
constant.
D) in all three dimensions: L, W, and H all increase at
the same rate.
30. Distinguish between internal vs external energy.
A) When you fill a mug of coffee, the internal energy
is the individual molecules moving around.
External energy would be the kinetic energy of the
cup as the barista slides it across the counter to
you.
B) Backwards! Internal energy would be the KE of the cup
sliding across the counter, but internal energy would be
the molecules moving.
C) Internal energy would be the KE of the cup sliding
across the counter. External energy would be the KE of
the barista’s hand as he pushes it.
D) Internal and external are just different ways to say
kinetic and potential. KE is always external energy, but
PE is always internal.
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P H Y S 1 4 0 0
SPRING
31. True or false: A swimming pool filled with water at 20°C
contains much more heat than a welding spark at 5000°C.
32. Two metal bars are brought into contact, end to end. One
bar has a temperature of 0°C, and the other is at 50°C.
A) Heat is exchanged in both directions, from hot to cold
and from cold to hot until both bars reach the same
final temperature.
B) The cold bar gives energy to the hot one until it comes
down to 0° to match the cold one.
C) The hot bar transfers heat to the cold one until
both reach a final temperature between 0° and 50°.
D) No heat is transferred in either direction, since metal is a
very poor conductor of heat.
33. True or false: Water has a very high specific heat when
compared to the specific heats of most metals.
34. How much energy (Q, in calories) is required to raise the
temperature of 10g of water (c = 1 cal/g·°C)from very cold
(Ti = 3°C) to a lukewarm temperature (Tf = 35°C)?
A) Q = 3 cal
C)
B) Q = 10 cal
D)
The cylinders shown
on the right all have
precisely the same
mass. They are all
heated to 100°C, then
placed on the block of
wax as shown. Each
cylinder melts the wax
until it reaches room
temperature (20°C).
Use the multiple
choices shown on the
figure to answer
Question37.
35. The cylinders
shown are brass,
iron, lead, and
tin. Identify which
cylinder is brass.
Brass = A
Q = 32 cal
Q = 35 cal
E)
F)
Q = 320 cal
Q = 350 cal
D
C
A
B
36. Conduction is
A) the transfer of heat via bulk motion of the medium.
B) the transfer of heat by electron and atomic
collisions.
C) the transfer of heat between objects that are not
actually touching.
D) the only way to transfer heat from a colder object to a
warmer one.
37. True or false: Solids are exceptionally good at heat
convection, while fluids tend to be poor convectors.
38. Latent heat of fusion is the amount of energy required to
completely change the phase of 1g of a substance
A) from liquid to solid.
D) either A or B is correct;
B) from solid to liquid.
the phase change can
C) from liquid to gas.
be in either direction.
2017
39. An ice cube tray is filled with liquid water at room
temperature (about 20°C) and placed in the freezer.
A) The temperature won't decrease, staying at 20°C, until
all the water has frozen into ice.
B) The water temperature decreases to the freezing
point (0°C) before the phase changes. Once the ice
freezes, then the temperature can then be
decreased more.
C) The temperature goes down by half, then half the water
freezes. The temperature of the remaining water goes
down by half again, then half of the liquid freezes. This
pattern repeats until all of the liquid has changed phase.
D) The process is totally random, so the temperature
decreases and phase changes or not. You can't ever
predict what will happen, only the final result: solid ice.
40. The specific heat of water is c = 1 cal/g·°C, and the the
latent heat of vaporization is Lv = 540 cal/g. You have 10g of
cool water initially at 15°C. How much total energy (Q) must
be added to completely vaporize the entire 10g of water?
A) Q = 1 cal/g·°C + 540 cal/g + 10 g + 15°C = 566 cal
B) Q = 540 cal/g + (100–15)°C = 625 cal
C) Q = (10g)(1cal/g·°C)(15°C)+(10g)(540cal/g) = 5850 cal
D) Q = (10g)(1cal/g·°C)(100–15°C)+(10g)(540cal/g)=6250cal
E) Q = (10g)(1cal/g·°C)(100–15°C)(540cal/g) = 459000 cal
41. Evaporation of a liquid is a cooling process. This means
that
A) the higher energy liquid molecules escape,
leaving the lower energy molecules behind.
B) the lower energy liquid molecules collide with and stick
to a cooler surface, and cool that surface.
C) the higher energy molecules give their energy to the
lower energy molecules, lowering the average energy
and thus the temperature of the liquid.
D) all of the liquid molecules have the same energy; it is a
cooling process because you have to put the liquid in
the refrigerator (or some kind of cooler) in order to start
the evaporation process.
42. True or false: Steel is an example of a very elastic material.
43. A mass m = 1kg stretches a spring by 3 cm (x = 0.03m). Use
Hooke’s Law to determine the spring constant k.
A)
B)
k = 0.03 N/m
k = 0.29 N/m
C)
D)
k = 1 N/m
k = 9.8 N/m
E)
F)
k = 100 N/m
k = 327 N/m
44. The sweep hand on a clock completes 1 full cycle every 60
seconds. What are the period and frequency of this motion?
A) T = 0.017s, f = 60Hz
D) T = 60s, f = 0.017Hz
B) T = 1s, f = 60Hz
E) T = 60s, f = 1Hz
C) T = 0.017s, f = 0.017Hz
F) T = 60s, f = 60Hz
45. A wave is
A) an oscillation in time only.
B) an oscillation in space only.
C) an oscillation in space propagated through time.
D) an oscillation in time propagated through space.
46. True or false: As a wave propagates, the medium is carried
along, also propagating in the same direction.
EXAM 02
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P H Y S 1 4 0 0
SPRING
47. A transverse wave propagates
A) parallel to the direction of the oscillation.
B) perpendicular to the direction of the oscillation.
C) neither parallel nor perpendicular to the propagation.
D) not at all. Transverse waves only oscillate (while
longitudinal waves only propagate).
Answer Questions 48–52 using the wave diagram below.
Answer each numeric question with exactly two decimal
places (no units!).
y (m)
A
0.40
0.20
1.0
0
1.4
0.60
–0.40
C
t (s)
B
48. Identify points A, B, and C on the figure above.
A) A: trough; B: node; C: crest.
B) A: node; B: trough; C: crest.
C) A: crest; B: trough; C: node.
D) A: trough; B: crest; C: node.
49. What is the amplitude of this wave?
50. What is the period of this wave?
A = 0.40m
T = 0.80s
51. What is the frequency of this wave? f = (1/0.80s)= 1.25Hz
52. If the wavelength of the above wave is measured to be
λ = 2.4m, what is the wave speed (remember that v = λf)?
A)
B)
v = 0.17 m/s
v = 1.92 m/s
C)
D)
v = 3.0 m/s
v = 6.0 m/s
53. For a sound to be audible to an average human, it must have
A) a frequency between 10–12Hz and 1Hz.
B) a frequency between 20Hz and 20,000Hz.
C) a frequency between 40kHz and 40MHz.
D) any frequency at all. Whenever molecules vibrate,
human ears hear them.
54. Dolphins can hear sound waves at very high frequencies–as
high as 40,000 Hz. A sound wave with this high frequency
would be labeled
A) infrasonic.
C) ultrasonic.
B) audible.
D) radiosonic.
EXAM 02
2017
55. What is the speed of sound through the vacuum of space?
A) Zero. Sound cannot travel through space.
B) Low, but not zero. Sound travels through space at the
same speed as it travels through air, v ≈ 340m/s.
C) High: sound travels through space at the same speed as
it travels through steel, about v ≈ 6000m/s.
D) Very high: sound travels through space at the same
speed as light travels, v = 3×108m/s.
56. Sound travels best through a medium that is
A) highly elastic, like steel.
B) extremely cold, like snow.
C) extremely dense, like lead.
D) amorphous and lightweight, like styrofoam.
57. Why does sound travel faster in warm air than cold?
A) It doesn't. Cold air is denser, so sound travels faster in
cold air.
B) Warm air is denser than cold, so sound travels faster.
C) Warm air molecules are moving faster than cold
air molecules, so sound travels faster.
D) Warm air is made of oxygen, and cold air is made of
nitrogen. Oxygen is a faster medium than nitrogen.
58. Why is humid air a faster medium for sound than dry air?
A) Because water is denser than air, and a denser medium
is always a faster medium.
B) Because air does not transmit sound waves at all; only
the water molecules actually transmit the sound energy.
C) Air molecules are heavier than water molecules.
With the same amount of kinetic energy, the
lighter water molecules have greater speed.
D) The speed of sound is exactly the same no matter what
the humidity or the temperature. The speed of sound is
a constant value through all media that transmit sound.
Air, water, steel—it’s all the same speed, about 340 m/s.
59. Refraction occurs when sound waves travel through air of
uneven temperatures. The sound waves will
A) continue to travel in a straight line.
B) bend away from the warm air toward cool air.
C) bend away from the cool air toward warm air.
D) resonate between cold and warm until they cancel out.
60. Constructive interference occurs when two waves are
A) in phase: crest1 matches crest2, and the resulting
wave has an amplitude A = A1 + A2.
B) out of phase: crest1 matches trough2, and the waves
cancel. Amplitude A = 0.
C) partially in phase, partially out of phase: the crests and
troughs are not perfectly aligned, which constructs a
new wave that looks nothing like either of the original
waves.
D) traveling in away from each other in two different
directions. The energy is then transmitted to a greater
area than if they were traveling in the same direction, so
it can be used for something constructive.
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