Quote:
Originally Posted by pANDAS Radio  They slow down in mid air, just towards the end of the rotation. |
that's just what happens. chuck a ball in the air and watch it.
[deeply boring] it's called a turning point; the direction of motion is in the opposite direction to the force applied (ie he's going
up but gravity is pulling
down) so he gradually slows (to a point where he's instantaneously motionless - or at least his arms n stuff might still be moving but his centre of mass is going neither up nor down) - then he starts moving in the other direction. "interestingly" his acceleration is always downwards even when he's moving up once he leaves the ball.
if you think of a ball thrown straight at a wall you can imagine easily that at a certain point about half way through the time it spends in contact with the wall it's momentarily stationary cos it's going from moving TOWARDS the wall to moving AWAY from it - it obviously can't be doing both at once so at the exact moment it changes it's doing neither.
the easiest place to see this is probably in a long pendulum like in a grandfather clock; at the end of each swing, where it changes direction, you can see it slow down. the acceleration in a pendulum is always directed towards the middle, which is also where it's moving fastest; at the outside it literally stops for a moment. the guy bouncing on the ball is doing the same kinda thing.
[/deeply boring]
