College physis exam questions

Anyone can help me do a problem set within 1 hour 50 min, March 17th, 2:30 pm-4:20 pm pacific time. The file attached is an example of the problem set for reference, not the one I need help on! 

Name:_______________________________________ Student ID _____________ Score _________
last first

Physics 115 – Practice Exam 3A 2

1. [7 pts] A heavily loaded boat is floating in a pond. The boat sinks because of a leak. What happens to
the surface level of the pond?

a. It stays the same.
b. It goes up.
c. It goes down.
d. More information is needed to reach a conclusion.

2. [7 pts] For a certain patient, the build-up of fatty tissue on the wall of an artery has decreased the

arterial radius by 10%. By how much would the pressure provided by the heart have to be increased to
maintain a constant volume of blood flow? Assume that the average flow velocity in the unconstricted
region is 50 cm/s and that the density of blood is 1060 kg/m3. Model the blood as an ideal
incompressible fluid.

a. 42 Pa
b. 71 Pa
c. 105 Pa
d. 91 Pa
e. 159 Pa

3. [7 pts] One way to heat a gas is to compress it. A gas at 1.00 atm at 25.0°C is compressed to one tenth

of its original volume, and it reaches 40.0 atm pressure. What is its new temperature?
a. 1500 K
b. 1 500°C
c. 1192°C
d. 919°C
e. 240°C

4. [7 pts] A brass cube, 10 cm on a side, is raised in temperature by 200°C. The coefficient of volume

expansion of brass is 57 ´ 10-6/K. By what percentage is any one of the 10-cm edges increased in
length?

a. 4%
b. 2.8%
c. 0.38%
d. 0.29%
e. 0.14%

5. [7 pts] An 80.0-g piece of copper, initially at 295°C, is dropped into 250 g of water contained in a 300-

g aluminum calorimeter; the water and calorimeter are initially at 10.0°C. What is the final temperature
of the system? (Specific heats of copper and aluminum are 0.092 0 and 0.215 cal/g×°C, respectively. cw
= 1.00 cal/g°C)

a. 12.8°C
b. 16.5°C
c. 28.4°C
d. 32.1°C
e. 42.7°C

Name: _______________________________________ Student ID _____________ Score _________
last first

Physics 115 – Practice Exam 3A 3

6. [7 pts] I place a 500-g ice cube (initially at 0°C) in a Styrofoam box with wall thickness 1.0 cm and
total surface area 600 cm2. If the air surrounding the box is at 20°C and after 4 hours the ice is
completely melted, what is the conductivity of the Styrofoam material? (Lf = 80 cal/g)

a. 9.6 ´ 10-5 cal/s×cm×°C
b. 2.8 ´ 10-6 cal/s×cm×°C
c. 1.15 ´ 10-2 cal/s×cm×°C
d. 2.3 ´ 10-4 cal/s×cm×°C
e. 7.4 ´ 10-4 cal/s×cm×°C

Consider the graph at right for questions 7 and 8.
The pV diagram at right illustrates four different processes which takes a
gas from state 1 to state 5. The process between state 3 and 4 is an
isothermal process.

7. [6 pts] Is the net work done on the gas positive, negative, or zero? Explain.
a. Positive
b. Negative
c. Zero
d. Not possible to answer

8. [6 pts] Rank the magnitude of the heat transferred with the gas in each of the four processes.

a. |”!→#| > |”$→%| = |”%→!| > |”&→$|
b. |”&→$| > |”!→#| = |”%→!| > |”$→%|
c. |”&→$| > |”!→#| > |”$→%| > |”%→!|
d. |”$→%| > |”%→!| = |”!→#| > |”&→$|

9. [7 pts] The electric dipole moment of the heart at a particular instant is

shown below right. Rank the following voltages from most positive to
most negative: %’ = %% − %&,%( = %! − %& and %) = %! − %$.

a. %) > %’ > %(
b. %’ > %) > %(
c. %) > %( > %’
d. %’ = %) > %(
e. %’ > %( > %)

10. [7 pts] As shown in the figure, three small charges are equally spaced on

the arc of a circle that is centered at the charge Q, where Q = +23 nC
and all the other quantities are accurate to two significant figures. What
is the magnitude of the net electric force on the charge Q due to the
other three charges?

a. 1.7 × 10*! N
b. 2.1 × 10*! N
c. 3.1 × 10*! N
d. 2.6 × 10*! N
e. 9.1 × 10*! N

Name: _______________________________________ Student ID _____________ Score _________
last first

Physics 115 – Practice Exam 3A 4

11. [6 pts] The square plates of a 3000-pF parallel-plate capacitor measure 40 mm by 40 mm and are
separated by a dielectric that is 0.29 mm thick and completely fills the region between the plates. What
is the dielectric constant of the dielectric?

a. 61
b. 56
c. 50
d. 45
e. 67

12. [6 pts] The figure shows an arrangement of two particles each having charge ” =

−6.8 nC and each separated by 5.0 mm from a proton. If the two particles are held
fixed at their locations and the proton is set into motion as shown, what is the
minimum speed the proton needs to totally escape from these particles? (6+,-.-/ =
1.67 × 10*$0 kg)

a. 2.2 × 101 m/s
b. 4.3 × 101 m/s
c. 8.3 × 101 m/s
d. 1.7 × 100 m/s

13. [6 pts] A number of resistors are connected across

points A and B as shown in the figure. What is the
equivalent resistance between points A and B?

a. 4 Ω
b. 6 Ω
c. 8 Ω
d. 10 Ω
e. 12 Ω

14. [6 pts] Series/Parallel Circuits: A 9-V battery is hooked up to two

resistors in series. One has a resistance of 5 Ω, and the other has a
resistance of 10 Ω. Several locations along the circuit are marked with
letters, as shown in the figure. Through which resistor is energy being
dissipated at the higher rate?

a. the 10-Ω resistor
b. the 5-Ω resistor
c. Energy is being dissipated by both resistors at the same rate.
d. Resistors do not dissipate energy, none of the above.

15. [6 pts] Three resistors connected in parallel have individual values of 4.0, 6.0 and 10.0 W, respectively.

If this combination is connected in series with a 12-V battery and a 2.0-W resistor, what is the current in
the 10-W resistor?

a. 0.59 A
b. 1.0 A
c. 11 A
d. 16 A

Name: _______________________________________ Student ID _____________ Score _________
last first

Physics 115 – Practice Exam 3A 5

16. [6 pts] For the circuit shown in the figure, calculate the
emf’s ℰ& and ℰ%, assuming that the batteries are ideal.
Note that two currents are shown.

a. ℰ& = 44 V, ℰ% = 28 V
b. ℰ& = 28 V, ℰ% = 44 V
c. ℰ& = 14 V, ℰ% = 22 V
d. ℰ& = 22 V, ℰ% = 14 V

17. [6 pts] A beam of electrons is sent in the positive x-direction in a region with a uniform magnetic field

B in the positive y-direction and a uniform electric field E in the positive z-direction. At which of the
following speeds would the electrons be deflected in the positive z-direction?

a. v < E/B b. v = E/B c. v > E/B
d. There is no speed for which this will happen.

18. [6 pts] The magnetic field at a distance of 2 cm from a long straight current-carrying wire is 4 μT. What

is the magnetic field at a distance of 1 cm from this wire?
a. 2 μT
b. 4 μT
c. 6 μT
d. 8 μT
e. 10 μT

19. [6 pts] A proton, mass 1.67 ´ 10-27 kg and charge +1.6 ´ 10-19 C, moves in a circular orbit

perpendicular to a uniform magnetic field of 0.75 T. Find the time for the proton to make one complete
circular orbit.

a. 4.3 ´ 10-8 s
b. 8.7 ´ 10-8 s
c. 4.9 ´ 10-7 s
d. 9.8 ´ 10-7 s

20. [6 pts] Two long parallel wires 20 cm apart carry currents of 5.0 A and 8.0 A in the same direction. Is

there any point between the two wires where the magnetic field is zero?
a. yes, midway between the wires
b. yes, 12 cm from the 5-A wire
c. yes, 7.7 cm from the 5-A wire
d. no

ℰ%
ℰ&

Name: _______________________________________ Student ID _____________ Score _________
last first

Physics 115 – Practice Exam 3A 6

Use the circuit at right to answer Questions 21 and 22

21. [6 pts] For the circuit shown in the figure and
using the directions of current specified, choose
the Kirchhoff current equation for the node labeled
A.

a. >& − >$ + >% = 0
b. >& + >$ + >% = 0
c. >& = >$ + >%
d. >& = −>$ + >%

22. [6 pts] Now choose the Kirchhoff loop equation for the entire outside loop. Notice the directions of the

currents!
a. %& − >%@% + %$ − >&@& = 0
b. %& − >%@% − %% + >&@& = 0
c. %& + >%@% − %% − >&@& = 0
d. %$ + >%@% + %% − >&@& = 0

23. [6 pts] RC Circuits: A charged capacitor is connected in

series with a resistor and an open switch. At time t = 0 s,
the switch is closed. Which of the graphs below best
describes the potential difference V across the capacitor
as a function of time t?

24. [6 pts] A circular metal loop of radius 10 cm and three long
straight wires carry currents of >& = 20 A, >$ = 50 A, >% = 20 A
and >! = 40 A, as shown in the figure. Each of the straight wires
is 20 cm from the center of the loop. The axes are shown in the
figure, with the +z-axis coming out of the paper. What is the y
component of the resultant magnetic field at the center of the
loop?

a. −54 CD
b. −60 CD
c. −50 CD
d. +60 CD
e. +50 CD

Name: _______________________________________ Student ID _____________ Score _________
last first

Physics 115 – Practice Exam 3A 7

25. [6 pts] Capacitors in Combination: A 5-µF, a 7-
µF, and an unknown capacitor E2 are connected in
parallel between points a and b as shown in the
figure. What do you know about the equivalent
capacitance E34 between a and b? (There could be
more than one correct choice.)

a. E34 > 12 µF
b. E34 > E2
c. 5 µF < E34 < 12 µF d. E34 < 5 µF e. E34 < E2

26. [6 pts] An air-filled capacitor carries enough charge to store 6.00 mJ of potential energy. It is then

accidentally filled with water in such a way as not to discharge its plates. How much energy does it
continue to store after it is filled? The dielectric constant for water is 78 and for air it is 1.0006.

a. 0.077 mJ
b. 468 mJ
c. 0.04 mJ
d. 6.00 mJ

27. [6 pts] A fully charged 37-µF capacitor is discharged through a 1.0-kΩ resistor. If the voltage across the

capacitor is reduced to 7.6 volts after just 20 ms, what was the original potential across the capacitor?
a. 16 V
b. 13 V
c. 11 V
d. 9.0 V
e. 8.0 V

28. [6 pts] A cell membrane has a resistance and a capacitance and thus a characteristic time constant.

What is the time constant of a 9.0-nm-thick membrane surrounding a 0.040-mm-diameter spherical
cell? I56547386 = 3.6 × 100Ω ⋅ 6,L56547386 = 9.0

a. 2.9 ms
b. 4.2 ms
c. 8.1 ms
d. 12 ms
e. 17 ms

29. [6 pts] Draw a circuit with two batteries, a resistor between them, and a capacitor in parallel with the
resistor. The batteries are connected negative pole to positive pole.

Name: _______________________________________ Student ID _____________ Score _________
last first

Physics 115 – Practice Exam 3A 8

30. [6 pts] A ring with a clockwise current (as viewed from above the ring) is situated with its center
directly above another ring, which has a counter-clockwise current, as shown in the figure. In what
direction is the net magnetic force exerted on the top ring due to the
bottom ring?

a. upward
b. Downward
c. to the left
d. to the right
e. The net force is zero.

31. [6 pts] Consider an ideal solenoid of length L, N windings, and radius b (L is much longer than b). A
current I is flowing through the wire windings. If the radius of the solenoid is doubled to 2b, but all the
other quantities remain the same, the magnetic field inside the solenoid will

a. remain the same.
b. become twice as strong as initially.
c. become one-half as strong as initially.
d. become four times as strong as initially.
e. become one-fourth as strong as initially.

Name: _______________________________________ Student ID _____________ Score _________
last first

Physics 115 – Practice Exam 3A 9

32. [6 pts] A positively charged particle moves through
a region with a uniform electric field pointing
toward the top of the page and a uniform magnetic
field pointing into the page. The particle can have
four velocities as shown. Rank the four possibilities
in order of decreasing magnitude of net force.:

a. |M&| > |M$| > |M%| = |M!|
b. |M$| = |M!| > |M%| = |M&|
c. |M&| > |M$| = |M!| > |M%|
d. |M&| > |M$| > |M!| > |M%|
e. |M$| = |M!| > |M&| = |M%|