Name:
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Physics 131 MCAT-Based Exam 1
Spring 2022
Cuyamaca College
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GUIDELINES:
1. The exam is over at 8 but you have until 8:15 p.m. to upload your solutions to the Exam 1 assignment in the Week
5 module. After that, canvas will be locked. You must show all your work (math, words, and pictures) in order to get
full credit. This includes conceptual questions.
2. Late submissions will be marked down ten points for turning in late.
3. If I find any evidence of the questions online (chegg, slader, ask yahoo, physics discussion boards, anything) then
everyone has to retake, and cheaters will get a zero and be referred to the Dean of Students. Please do not risk this.
4. You can work alone or with ONE other person from class. Open notes and text, but no internet or googling or
group chats. No two groups can work in the same space. Each partner must turn in their own exam.
5. I will be available for questions, but please only clarifying questions! Not: did we do this right?
6. Good luck!
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1. You and your 30kg kid brother decide to play a game. You tell him that he can levitate if
you can create an electric force that perfectly balances out his weight when he jumps
from a tree that is 10m tall. He just has to hold a bag of positive charge and you need to
hold an equal bag of positive charge right beneath him. How much charge must be in
each of your bags if your brother is to levitate when he jumps from the 10m high branch?
a. 3×10-4 C
b. 9×10-4 C
c. 1.8×10-3 C
d. 1 C
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2. If the electric field at a distance r away from a charge Q is 36 N/C, what is the ratio of the
electric fields at r, 2r, 6r?
A)
B)
C)
D)
9:3:1
36:9:4
36:9:1
36:18:12
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3. Find the electric potential one millimeter away from an oxygen nucleus?
A)
B)
C)
D)
1.4 x 10-9 V
8.6 x 10-6 V
1.2 x 10-5 V
8.6 x 10-3 V
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4. As you know, neurons are essentially the wires in the body that send electrical impulses so that
signals can be sent throughout the body. This electric signal happens when ions suddenly rush
into an ion channel in the neuron’s cell wall and propagate down the axon of the neuron.
Measurements have shown these “action potentials” happen when the potential difference
between the inside and outside of the neuron reaches about 80mV. If the thickness of the neuron
cell wall is 5 micrometers, what would be the strength of the electric field inside the ion channel?
a.
b.
c.
d.
50 N/C
200 N/C
8000 N/C
16000 N/C
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5. Free response question: You are at your three year old niece’s birthday party and she asks
you to explain why the balloon sticks to the wall after you rub it on her hair. She is a very
specific little girl and wants you to explain using BOTH words and pictures and to use the
words: charge, repel, and polarization. And she also wants it to be in your own words, not what
that crazy bald physics professor wrote in his solutions.
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6. Two oppositely charged particles are placed near each other. At the point halfway between the
two positive charges, what best describes the electric field and electric potential at that point.
Explain your answer using pictures and words.
a.
b.
c.
d.
The electric field is zero and the potential is positive.
The electric field is zero and the potential is zero.
The electric field is not zero and the potential is positive.
The electric field is not zero and the potential is zero.
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7. What is the net electric potential at point P due to
the four charges shown if q = 10 nC and d = 2.00
cm?
a.
b.
c.
d.
1492 V
1912 V
2001 V
2250 V
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8. At his peak, former California governor and bodybuilder Arnold Shwartzenegger, had an arm
that was 16cm in diameter and 1m long. If you were to connect each end of his arm to a 9V
battery, what current would run through it? (The resistivity of the human arm is about 17,000
ohm-meters).
a.
b.
c.
d.
11 micro-ohms
22 micro-ohms
33 micro-ohms
44 micro-ohms
8
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