2011-06-16 HW 2.pdf

HW #2
Assigned Wednesday June 16
Due: Monday June 20 Recitation 9AM

Problem 1
A particle (charge = +40 µC) is located on the x axis at the
point x = -20 cm, and a second particle (charge = -50 µC) is
placed on the x axis at x = +30 cm. What is the magnitude of
the total electrostatic force on a third particle (charge = -4.0
µC) placed at the origin (x = 0)?
a. 41 N
b. 16 N
c. 56 N
d. 35 N
e. 72 N

Prob. 23-36
Problem 2
A uniformly charged rod of length L and total charge Q lies
along the x-axis as shown in the figure.
(a) Find the components of the electric field at the point P
on the y-axis a distance d from the origin.
(b) What are the approximate values of the field
components when d >> L? Explain why you would
expect these results.

Problem 3
Prob. 23-10
Two small metallic spheres, each of
mass m = 0.200g are suspended as
pendulums by light strings of length L
as shown in the figure. The spheres are
given the same charge of 7.2 nC, and
they come to equilibrium when each
string is at an angle of θ = 5.00 o with
the vertical.
How long are the strings?

Problem 4
Prob. 23-49
A proton moves at 4.5 x 10 5 m/s in the horizontal direction. It enters a
uniform vertical electric field with a magnitude of 9.60 x 10 3 N/C.
Ignoring any gravitational effects, find
(a) the time interval required for the proton to travel 5.00 cm
horizontally
(b) its vertical displacement during the time interval in which it travels
5.00 cm horizontally
(c) the horizontal and vertical components of its velocity after it has
traveled 5.00 cm horizontally.