Download Test 1 - Al Akhawayn University

School of Science and Engineering
Al Akhawayn University
Exam# 1
Phy1402-01, Summer 2001
Instructor: Dr. H. Darhmaoui
Date: June 19, 2001
1. Two large parallel plates having equal but opposite charge are separated by 12.0 cm. Each plate
has a surface charge density of 36.0 nC/m2. A proton is released from rest at the positive plate.
Determine:
a. The potential difference between the plates.
b. The speed of the proton just before it strikes the negative plate.
c. Using kinematics, find the acceleration of the proton between the plates.
d. From (c), find the net force on the proton.
e. From the force, find the electric field intensity and show that it is equal to the electric
field intensity found from the charge densities of the plates.
(ε0 = 8.854 10-12 C2/N m2 , k= 1/(4π ε0) = 9 109 Nm2/C2 , Charge of the proton: e = 1.602 10-19 C,
mass of the proton: mp = 1.672 10-27 kg )
2. Two hollow conducting spheres have a common center
(Figure 1). The dimensions of the spheres are:
Sphere 1: inner radius Ra= 0.30 m, outer radius Rb= 0.32 m
Sphere 2: inner radius Rc= 0.89 m, outer radius Rd= 0.91 m
A charge of –100 nC is placed on the inner conductor and a
charge of +60 nC is placed on the outer conductor.
a. Find the charges on the inner and outer surfaces of both
spheres
b. Find the electric field at the following positions: r =0.25
m, 0.31 m, 0.40 m, 0.90 m and 0.95 m.
rc
ra
rb
Figure 1
3. A bock with a speaker attached to it is connected to a spring
having a spring constant k = 20.0 N/m as in Figure 2. The total
mass of the block speaker is 5.00 kg, and the amplitude of this
unit’s motion is 0.500 m. (assume that the speed of sound is 343
m/s)
a. If the speaker emits sound waves of frequency 440 Hz,
determine the range in frequencies heard by the person
to the right of the speakers.
b. If the maximum intensity heard by the person is 60 dB
when he is closest to the speakers, 1.00 m away, what is
the minimum intensity level heard by the observer?
4. Two speakers are driven by the same oscillator of frequency
200 Hz. They are located on a vertical pole a distance of 4.00
m from each other. A man walks toward one of the speakers in
a direction perpendicular to the pole as shown in Figure 3.
(take the speed of sound to be 330 m/s and ignore any sound
reflections coming from the floor)
a. How many times will he hear a minimum in sound
intensity?
b. How far is he from the wall at these moments?
Figure 2
Figure 3
rd