Spring 2001 Physics 101 Hour Exam 3
(25 questions)

The grading button and a description of the scoring criteria are at the bottom of this page. Basic questions are marked by a single star *. More difficult questions are marked by two stars **. The most challenging questions are marked by three stars ***.

This exam consists of 25 questions; true-false questions are worth 2 points each, three-choice multiple choice questions are worth 3 points each, five-choice multiple choice questions are worth 6 points each. The maximum possible score is 112. When the exam was given, the mean was 98.7; the median was 101. Click here to see the formula sheet that came with the exam.


QUESTION 1*

What temperature has the same value in both the Fahrenheit and Celsius scales?

(a)   -10
(b)   -20
(c)   -40
(d)   -50
(e)   -60


QUESTION 2**

A steel tape measure is marked in such a way that it gives accurate length measurements at 20 C. Suppose this tape measure is used on a cold day when the temperature is 0 C. Assuming that the object you are measuring has a much smaller linear expansion coefficient than steel, the length measured with this tape measure will be

(a)   too long.
(b)   too short.
(c)   accurate.


QUESTION 3*

A washer has a hole in the middle of it. As the washer is heated, the size of the hole decreases.

(T)   True
(F)   False


QUESTION 4*

A copper flask with a volume of 150 cm3 is filled to the brim with olive oil. The coefficient of volume expansion is 51 x 10-6 C-1 for the flask and 680 x 10-6 C-1 for the olive oil. If the temperature of the system is increased from 6 C to 31 C, how much oil overflows from the flask?

(a)   10 cm3
(b)   15 cm3
(c)   2.4 cm3
(d)   5.2 cm3
(e)   7.8 cm3


QUESTION 5*

Block A has a mass M and an initial temperature of 0 C. Block B has a mass of 2M and an initial temperature of 100 C. Both blocks are made of the same material. Now the blocks are brought into thermal contact, so that they both end up at the same final temperature T. Assuming no heat is lost to the surroundings, then

(a)   T > 50 C
(b)   T = 50 C
(c)   T < 50 C


QUESTION 6*

The specific heat of alcohol is about half that of water. Suppose you have identical masses of alcohol and water. The alcohol is initially at temperature TA. The water is initially at a different temperature TW. Now the two fluids are mixed in the same container and allowed to come into thermal equilibrium, with no loss of heat to the surroundings. The final temperature of the mixture will be

(a)   closer to TA than TW.
(b)   closer to TW than TA.
(c)   exactly halfway between TA and TW.


QUESTION 7*

It takes a certain amount of time to boil away a pot of water. How long would it take to boil away the same pot of water if the applied heat rate was the same but the latent heat of vaporization of water was larger?

(a)   It would take more time.
(b)   It would take less time.
(c)   It would take the same time.


QUESTION 8*

A metal cup has mass 0.12 kg and initial temperature 20 C. Into this cup is poured 0.30 kg of water (specific heat 4190 J/kg-C) , which is initially at temperature 70 C. The final temperature of the cup-water system is 66 C. Assuming no heat is lost to the surroundings, what is the specific heat of the cup.

(a)   150 J/kg-C
(b)   300 J/kg-C
(c)   460 J/kg-C
(d)   910 J/kg-C
(e)   5200 J/kg-C


QUESTION 9*

You have a large styrofoam container containing 5 kg of ice (specific heat = 2000 J/kg-C) at -20 C. You want to add just enough water (specific heat = 4190 J/kg-C) at an initial temperature of 25 C so that the final temperature of the system is 0 C with all the ice melted. The latent heat of fusion of water is 3.34 x 105 J/kg. How much water should you add?

(a)   18 kg
(b)   25 kg
(c)   9.5 kg
(d)   2.7 kg
(e)   1.4 kg


QUESTION 10*

This and the following two questions concern the same physical situation.

A submarine has a small window of total area 0.0148 m2. Calculate the total pressure force on the window when the submarine is at a depth of 110 m. Neglect atmospheric pressure. You may assume that the density of the surrounding fresh water is 1000 kg/m2.

(a)   5000 N
(b)   11000 N
(c)   16000 N
(d)   23000 N
(e)   37000 N


QUESTION 11*

Suppose the submarine dives to twice the depth. The force on the window

(a)   stays the same.
(b)   increases by a factor of two.
(c)   increases by a factor of four.


QUESTION 12*

Now suppose that the submarine dives in salt water, which has higher density, to a depth of 110m. If your answer to the original question is F, the pressure force on the window is now

(a)   greater than F.
(b)   less than F.
(c)   the same (F).


QUESTION 13*

This and the following two questions concern the same physical situation.

NASA builds a raft made of styrofoam that can just support the weight of three astronauts without submerging. The weight of each astronaut is 733 N. Neglecting the weight of the raft itself, which is very light, what is the volume of the raft?

(a)   0.11 m3
(b)   0.22 m3
(c)   0.44 m3
(d)   1.20 m3
(e)   1.50 m3


QUESTION 14**

The raft is now transported to Mars. After being loaded with the same three astronauts in the Mars colony swimming pool where g = 3.73 m/s2, will the raft now

(a)   sink in the water.
(b)   float higher in the water.
(c)   float at the same height in the water.


QUESTION 15*

Assuming that water is incompressible, the buoyant force on a swimmer diving to the bottom of a pool is __________ the buoyant force on a swimmer who dives just below the surface of the water but is still fully submerged.

(a)   less than
(b)   more than
(c)   the same as


QUESTION 16*

A hydraulic lift with a circular output plunger of radius 0.5 m is used to lift a building of mass 10,000 kg. The input plunger (which is at the same height as the output plunger) has radius 0.01 m. How much force must be exerted on the input plunger to support the building?

(a)   18 N
(b)   39 N
(c)   160 N
(d)   1600 N
(e)   9800 N


QUESTION 17*

A major Midwestern university is redesigning its air conditioning system because both faculty and students complain that every spring, when the weather turns warm, it takes almost a week for the heating system to turn off and the cooling system to turn on. Ideally the designers would like to deliver chilled water to each building on campus at a rate of 0.1 kg/s through a pipe of radius 1 cm. At what speed will water need to flow through the pipe?

(a)   0.3 m/s
(b)   0.4 m/s
(c)   0.5 m/s
(d)   0.6 m/s
(e)   0.7 m/s


QUESTION 18**

This and the following question concern the same physical situation.

Many small sailboats use a passive bailing system: there is a plug in the bottom of the boat that can be opened to drain water out of the boat. This works only when the boat is moving, because only then is the pressure under the boat less than air pressure, by Bernoulliís equation.

Consider a boat whose bailing plug is located 3 cm below the surface of the water. What is the minimum speed the boat must have so all the water drains out of the boat?

(a)   0.25 m/s
(b)   0.5 m/s
(c)   0.75 m/s
(d)   1.0 m/s
(e)   1.25 m/s


QUESTION 19**

Now consider a boat with bailing plug located 6 cm below the surface of the water. If your answer to the previous question is v, then the minimum speed for this boat is

(a)   v
(b)   1.4 v
(c)   2 v


QUESTION 20*

This and the following two questions concern the same physical situation.

On a horizontal frictionless table, a block of mass 0.1 kg is attached to a spring of constant k = 5 N/m and set into oscillation with amplitude A = 0.30 m.

What is the frequency of oscillation of this system?

(a)   1.13 Hz
(b)   0.75 Hz
(c)   2.44 Hz
(d)   0.21 Hz
(e)   1.97 Hz


QUESTION 21*

What is the maximum kinetic energy of the mass?

(a)   0.12 J
(b)   2.12 J
(c)   1.05 J
(d)   0.23 J
(e)   0.85 J


QUESTION 22*

Let Emax be your answer to the previous question. If you now replace the block with a 0.2 kg block but keep the spring and the oscillation amplitude the same, the maximum kinetic energy of the block will be 2Emax.

(T)   True
(F)   False


QUESTION 23*

This and the following two questions concern the same physical situation.

You have in your toolbox a 0.25 kg mass and a ball of string. You want to make a pendulum that has a period of 0.5 seconds.

How long a string should you cut to make your pendulum? (You can neglect the mass of the string.)

(a)   6 cm
(b)   15 cm
(c)   28 cm
(d)   39 cm
(e)   47 cm


QUESTION 24*

Let your answer to the previous question be L. If you were on the moon what length of string should you use? (The gravity on the moon is 6 times smaller than the gravity on Earth.)

(a)   L/6
(b)   L
(c)   6 L


QUESTION 25*

A 1.2 kg mass is hanging vertically on a spring. You pull the mass down and release it. The mass goes up and then down. It takes the mass 0.58 seconds to go all the way back down to the position where you released it for the first time. What is the spring constant?

(a)   30 N/m
(b)   90 N/m
(c)   140 N/m
(d)   200 N/m
(e)   250 N/m