"Constant velocity" means zero acceleration, which means zero net force. So there must be100N pulling on the crate to cancel the 100N of friction force.
Answer:
4.39 x 10^-19 J
Explanation:
q1 = 1.6 x 10^-19 C
q2 = - 1.6 x 10^-19 C
r1 = 3 x 10^-10 m
r2 = 7 x 10^-10 m
The formula for the potential energy is given by
U1 = k q1 q2 / r1 = - (9 x 10^9 x 1.6 x 10^-19 x 1.6 x 10^-19) / (3 x 10^-10)
U1 = - 7.68 x 10^-19 J
U2 = k q1 q2 / r2 = - (9 x 10^9 x 1.6 x 10^-19 x 1.6 x 10^-19) / (7 x 10^-10)
U2 = - 3.29 x 10^-19 J
Change in potential energy is
U2 - U1 = - 3.29 x 10^-19 + 7.68 x 10^-19 = 4.39 x 10^-19 J
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