A 120 N child is in a swing that is attached to ropes 2.20 m long. Find the gravitational potential energy of the child-Earth system relative to the child's lowest position at the following times.

Question

(a) when the ropes are horizontal

(b) when the ropes make a 29.0° angle with the vertical

(c) when the child is at the bottom of the circular arc

Answer 1

(a) M*g*R
(b) M*g*R (1 - cos 29)
(c) zero

In this case, M g = 120 N

Answer 2

(a) 264
(b) 461.49
(c) 0

Answer 3

(a) =F*h
120*2.2= 264
(b)264*(1-cos29)
=33.1
(c)zero