Download Test 1 - Al Akhawayn University

School of Science and Engineering
Al Akhawayn University
Test # 1
Phy1402, Fall 2002
Instructor: Dr. H. Darhmaoui
Date: October 18, 2002
1) A student holds a tuning fork oscillating at 256 Hz. He walks towards a wall at a constant speed of
1.33 m/s. (Assume that the speed of sound in air is 344 m/s)
(a) What beat frequency does he observe between the tuning fork and its echo?
(b) How fast must he walk away from the wall to observe a beat frequency of 5Hz?
2) Two small spheres each of mass m = 2.00 g are suspended by light
strings 10.0 cm in length (Figure 1). A uniform electric field is applied
in the x direction. If the spheres have charges equal to -5.00 10-8 C and
+5.00 108 C, determine the electric field that enables the spheres to be in
equilibrium at an angle θ = 10°.
Figure 1
3) On planet Tehar, the gravitational field strength is the same as that on Earth (g = 9.81 m/s2) but
on Tehar there is also a strong downward electric field that is uniform close to the planet’s
surface. A 2.00-kg ball carrying a charge of 5.00 µC is thrown upward at 20.1 m/s and hits the
ground after 4.10 s. What is the potential difference between the starting point and the top point
of the trajectory?
4) Two hollow conducting spheres have a common center
(Figure 2). 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.
Figure 2
rc
ra
rb
rd
Solution