Question

What happens to the kinetic and potential energy as two electrons move closer to one another? A:
2. Is the force between an electron and a proton as they come closer together attractive or repulsive? A:
3. When two bar magnets are placed end-to-end they repel each other. What does that tell us about their charges? A:

Answer 1

1. Two electrons are like charges, so their electric potential energy U = k q1 q2 / r is positive and increases as r decreases. To bring them closer you must do work, so their kinetic energy decreases (for an isolated pair without external input, ΔK = −ΔU).

2. An electron and a proton have opposite charges, so the force between them is attractive. The attraction gets stronger (larger magnitude) as they come closer.

3. Magnetic poles behave like "charges" for magnetism: like poles repel and unlike poles attract. If two bar magnets placed end-to-end repel, the facing ends are the same pole (both north or both south) — it does not mean they have electric charge.