haruspex's latest activity

Think about the connection between those observations.

It is stated as frictionless, but it makes no difference anyway.

Sure, but that’s just two plates. What if, e.g., we start with two positively charged plates then add a grounded plate, not between...

The tension is at different angles in different places. Where will its y component be mg? No, the tension will keep changing. Often...

First, think about the equilibrium position. Can you draw that? Clearly the centre mass will keep descending as long as it is above...

It is the model everyone uses, e.g...

The effect of a force F on a mass m in time ##dt## is to accelerate it by ##dv=F\cdot dt/m##. If instead the force is ##F-dF## then the...

This is what I am missing. How does that follow?

But I don’t see a valid argument for that in the concentric sphere model. A single infinite charged plate clearly exerts a field on...

It might help to treat the mouth in more detail. Say it is a smooth quadrant of radius ##r##. We are interested in the limit as...

Ok, good. But I do wonder what happens if it's an extensible string. Such cases can be confusing.

Indeed, a standard example being the charge a point charge induces on a grounded sphere.

Doesn’t that result in the solution in post #11? But I am uncomfortable with this question. Infinite plates and potentials is an...

You may have misunderstood what @TSny was asking, which was to write an expression for ##dt## in terms of ##dK##. And you have that, in...

If a rod spins about its midpoint, each end is accelerating towards the centre.