PHYSICS 101/102
Spring 2012
EXAM 3 Takehome
Name _________________
Section ___101 102____
IT WOULD BE WISE TO READ THE FOLLOWING - IT WILL GREATLY IMPACT THE GRADING.
BECAUSE THIS IS A TAKEHOME EXAM, THE "RULES" WILL BE ABSOLUTELY ENFORCED.
After reading each rule please initial so that your paper will be graded:
Numbers alone will not count - include the physics to justify the numbers. Any numbers used must be part of a
physics law or principle, part of the given information or developed from a law or given information. initial_____
Don't do the arithmetic in your head, do it on the paper
initial_____
If a question asks for an explanation, errors in the explanation can forfeit the points even for an
initial_____
otherwise correct “answer.”
Underline or box your numerical answers to indicate your final answers for numerical problems
Initial_____
Any question I do not attempt to answer (leave blank) will cause points to be subtracted.
initial_____
1.
A rectangular barge, 5 m long and 2 m wide, floats in fresh water. You are going to find how much deeper it
floats when it has a certain additional load.
a. What physics will you use to do this? Mention all of the physics.
( 4 points)
b. Find how much deeper it floats when its load is a 400-kg horse.
( 2 points)
H=
c. If the barge can only be pushed 15 cm deeper into the water before water overflows to sink it, how many
400-kg horses can it carry?
( 2 points)
#=
2.
On a perfectly still day, a hot-air balloon is hovering at low altitude. It is not going up or down. The total
weight of the balloon, including its load and the hot air in it, is 20,000N.
a. What physics will you use to find the weight and volume of the displaced air?
( 3 points )
b. What is the weight of the displaced air?
( 1 point)
W=
c. What is the volume of the displaced air?(use g = 10m/s2 and ρair = 1.2kg/m3)
( 1 point)
V=
Page 1 of 4
PHYSICS 101/102
3.
EXAM 3 Takehome
Spring 2012
The density of ocean water is 1.025 g/cm3 and an object with density 0.98 g/cm 3 is floating in the water. You
are to determine what percent of the object's volume is submerged.
a. Explain how you will do this (NO CALCULATIONS HERE)
(2 points)
b.
Do the calculations
(1 point)
%=
4.
Two point charges are separated by 1 m. The electrical force between them is 25 N. What will be the force
(in Newtons) between them when they are separated by 3 m, one of the charges is doubled and the other
charge is tripled?
( 3 points)
F=
5.
The potential difference between a Van der Graff generator and your hand is 50,000volts. You are going to
find the change of potential energy of the charge of 10-5C if it flashes in a spark from generator to your hand.
.
a. What physics will you use to do this?
( 3 points )
b. Calculate the change of potential energy.
( 1 point)
ΔEPE =
6.
A certain light bulb with a resistance of 322 ohms is labeled “150W." Was this bulb designed for use in a 120V
circuit or 220V circuit? Don't just guess - prove it!
( 3 points)
Page 2 of 4
PHYSICS 101/102
7.
EXAM 3 Takehome
Spring 2012
Calculate (a) the current drawn by and (b) the resistance of a 1200W hair dryer connected to 120V.
a. Current (show me the physics, not just numbers, before the calculation):
( 2 points )
I=
b. Resistance (show me the physics, not just numbers, before the calculation):
( 2 points )
Ω=
8.
9.
Will a closely spaced but not touching pair of parallel current-carrying wires exert forces on each other?
EXPLAIN
( 3 points )
Which of the fields (electric or magnetic) in a "high energy accelerator" can increase the speed of the charged
particles? Explain your answer fully
10. Is the current going into the page or out of the page?
( 2 points )
Explain how you know.
Into or Out of page
circle one
11. Is the current in the wire flowing to the top of the wire or to the bottom of the wire?
Explain how you know
to TOP or to BOTTOM of page
circle one
Page 3 of 4
( 2 points )
PHYSICS 101/102
EXAM 3 Takehome
12. Which way will the proton beam be deflected after going through the magnetic field?
| |
| |
|S |
Explain how you know
p+ =====>
. .
|N|
| |
| |
Page 4 of 4
Spring 2012
( 2 points )