Monday
May 2, 2016

Homework Help: Physics

Posted by Papito on Tuesday, May 8, 2007 at 9:28am.

A trapeze artist, starting from rest, swings downward on the bar, lets go at the bottom of the swing, and falls freely to the net. An assistant, standing on the same platform as the trapeze artist, jumps from rest straight downward. Friction and air resistance are negligible.

(a) On which person, if either, does gravity do the greatest amount of work?
*the person with more mass
*trapeze artist
*assistant

Explain

(b) Who, if either, strikes the net with a greater speed?
assistant
trapeze artist
neither

My solution
a) I say more work is done on the assistant because as he moves upwards he resists gravity, thus more work is required to overcome the resistance.

b) trapeze artist

(a) It is not clear from the workding of your question whether the platform is at the elevation where the trapeze artists begins or ends his swing. If they begin at the same elevation, gravity does more work on the more massive person. The trapeze does no work while it is held, because motion is perpedicular to the tension force in the trapeze ropes.
(b) neither The kinetic energy is propertional to mass, but mass gets divided out when computing velocity.
Not all of the trapeze artist's velocity will be vertical

So if I understand this , u meant the body with vertical displacement has more speed, which would be the assistant since he jumps (vertically) downward

No, that is not what I meant. They both have the same speed (and KE), but the trapeze artist has some of that speed directed horizontally due to the time he spent swinging forward on the trapeze.

So with that said it means the trapeze artist will land with a lesser speed because some of his speed is directed horizontally. Thanks