Introductory Physics Volume Two

1.8 Homework 33
⊲ Problem 1.14
Richard Feynman said that if two people were at arm’s length from
each other and each person had 1% more electrons than protons, the
force of repulsion between them would be about equal to the “weight”
of the entire Earth. Was Feynman exaggerating?
⊲ Problem 1.15
A point charge q is at the position (x 0 , y 0 ). Find the electric field at
an arbitrary point (x, y) due to the charge q.
⊲ Problem 1.16
Two 2.0 µC charges are located on the x axis at x = 1.0m and at
x = −1.0m.
(a) Determine the electric field on the y axis at y = 0.5.m.
(b) Calculate the electric force on a −3.0µC charged place at this point.
⊲ Problem 1.17
A uniformly charged insulating rod of length 14 cm is bent into the
shape of a semicircle. If the rod has a total charge of −7.5µC, find
the magnitude and direction of the electric field at the center of the
semicircle.
⊲ Problem 1.18
An electron moves at a speed of 3 × 10 6 m s
into a uniform electric field
of magnitude 1000 N/C. The field is parallel to the electron’s velocity
and acts to decelerate the electron. How far does the electron travel
before it is brought to rest?
⊲ Problem 1.19
A proton moves at 4.5 × 10 5 m s
in the horizontal direction. It enters a
uniform electric field of 9.6 × 10 3 N/C directed downward. Ignore any
gravitational effects and find the time it takes the proton to travel 5.0
cm horizontally, its vertical displacement after it has traveled 5.0 cm
horizontally, and the horizontal and vertical components of its velocity
after it has traveled 5.0 cm horizontally.
⊲ Problem 1.20
y
x
θ
E