Answer:
21813.46 J
Explanation:
The Potential energy stored at the time it is hanging freely is mgl.
the potential energy stored at the time when it makes a angle 23 degree from the vertical is mglCos 23
Change in gravitational potential energy
U = mgl = mgl cos 23
U = mgl (1 - cos23)
U = 1400 x 9.8 x 20 ( 1 - Cos 23)
U = 21813.46 J