# physics

posted by
**bobpursley**
.

Draw the figure, and calcuate the height above the bottom point the swing starts. (I remember it as 2.3(1-cos25)).

the initial energy is mg*height.

The final energy is 1/2 m v^2

The difference is frction.

A 49 kg child on a 2.3 m long swing is released

from rest when the swing supports make an

angle of 25 degrees with the vertical.

The acceleration of gravity is 9.8 m=s2 :

If the speed of the child at the lowest po-

sition is 1.83818 m=s, what is the mechani-

cal energy dissipated by the various resistive

forces (e.g. friction, etc.)? Answer in units of

J.