Recent content by haruspex

As stated in post #1, @palaphys knows how to solve the problem. The question being asked of the forum is why the suggested alternative method does not work. An interesting corollary is that a flat base viewed through a uniform depth of water does not appear flat. So what shape does it appear...

Not quite that simple. When you put your finger on the top the air pressure is still atmospheric: same number of molecules at the same temperature in the same volume. But what happens as you lift the straw? No, the pressure at the surface of the surrounding water is still atmospheric. The...

Then I confirm your results. What would the net flux be if they were both +q and equidistant on opposite sides? (Consider symmetry.) Consider one point charge on the ring. What flux does it generate through the ring (and not in the plane of the ring)?

A free body diagram shows the forces on a single rigid body. Here you have a linkage, so you need an FBD for each moving part. This will involve defining unknowns for forces and torques between connected bodies, each such force being represented in the FBDs for both bodies. What are the moving...

Do you mean, you don’t know if it is the smallest mass that would cause them to slide up? Why does that matter? What allows you to treat them as one unit is the information that "m2 remains at rest with respect to m1". That is, they behave exactly as if they were glued together.

Ok, I'll give you that one.

No, that doesn’t work either. You cannot add angular velocities that are around different axes. What axis would the resulting angular velocity be about? At any instant, there may be points on the sphere that are moving directly towards or directly away from C, while others may be moving in...

Good. That's unlikely to work. Energy conservation equations are time independent . No, you can't do that. The motion of a rigid body at an instant can be expressed as the sum of the linear motion of its mass centre and its angular rotation about that centre. There is nothing more to add...

Right

The arrows on the airflow show the relative motion. If the air is actually still, which way is the ball moving?

I have a feeling I have misled you on statement 1. From experience, there should be downward pressure on the ball. And if the air is moving faster under the ball the pressure must be lower there. Yes. I mean the ball is moving sufficiently fast that you can ignore the wind and treat the air...

Yes, and the reasoning you give is ok. I would have described it as the flow lines are compressed below so the air pressure is greater. Surely the flow lines are as they are because of the ball's rotation. To see the effect of opposite spin, just flip the picture upside down. I think you are...

If ##x=y ## then ##x^2=y^2##. If ##10cm=(1/10)m## then what is ##(10cm)^2##?

Yes, you do seem to have a sign error in post #59, but where exactly it is depends which sense you are taking as positive for each variable. Please state that for each of ##\omega_C, \omega_{cm}, L, \alpha_C, \tau_C##.

If you mean compared with what I posted in post #60, I only meant that your numerator/denominator term reduced to that. I dropped the minus sign that preceded it. ##\alpha_C## should be negative, right?