Document Preview: Physics 202, Homework #1
Due: Wednesday, 09/11/2013 at 10:50 AM
1. In the figure below, q = -2e, q = +2e, q = +4e, and q = +2e, where e is the elementary
1 2 3 4
charge. Charge q is located at the origin, while q and q are each a distance d = d =
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(2d)/3 from the origin. Charge 1 is a distance d = d from the origin. The dashed line
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connecting charge 1 and charge 4 makes an angle ? with respect to the negative x
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direction. Our goal is to find the net electric force on charge q .
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a. Let be the force that q exerts on q , be the force that q exerts on q , and
1 4 2 4
be the force that q exerts on q . Draw vectors on the figure above that indicate
3 4
the direction of each of these three forces (i.e. draw a free body diagram).
Remember to label each vector. (3 points)
b. Determine , , and in unit vector notation. Put your answers in terms of
d, ? , and physical constants. (3 points)
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c. Determine the net force exerted on q in unit vector notation. Put your answer
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in terms of d, ? , and physical constants. (2 points)
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d. Determine the magnitude of . Put your answer in terms of d, ? , and physical
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constants. (2 points)2. In the figure below, a non-conducting rod has a length L and a charge –q uniformly
distributed along its length. Point P is a distance a from the right edge of the rod. Our
goal in this problem is to find the electric field (both magnitude and direction) at point P.
Assume that positive x is to the right.
a. What is the direction of the electric field at point P? (2 points)
b. Determine the linear charge density. Put your answer in terms of q, L, a, and
physical constants. (1 point)
c. Determine the electric field due to a differential element of width dx, that is
located a distance x from the left side of the rod. In other words, x = 0 at the left
side of the rod. Put your answer in terms of q, L, a, x, dx, and physical constants....