8 questions (Essentials of physics)

8 questions of physics


Use (10.1.1) with r = 0.01m. We’re told that q1 = q2, so you can replace q2 by q1 and then solve for q1.


Again use (10.1.1). You don’t need to know the result of the last problem. We know what the force at r = 0.01m is: F = 0.001N. Now we want to increase the distance to rnew = 0.05m. To find out how this changes the force, form the ratio between the unknown new force and the previous force:

Fnew =? F

The charges q1 and q2 in the formula for Fnew and F are unchanged, so q1 and q2 cancel in the ratio on the right-hand side. Only the ratio between r and rnew will appear – and you know its value. You should get a force that’s a lot smaller than F from problem 1.


Again use (10.1.1). The mass in kg isn’t relevant to the answer.


Again use (10.1.1), making sure to use meters and not km for the distance r. Also state if the force is force is attractive or repulsive.


Again use (10.1.1): solve for r. 7

Use (10.2.1)


Again use (10.2.1): solve for the field by dividing both sides by the charge (also specify the direction of the field).

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