A 80- kg child sits in a swing suspended with 2.6- m-long ropes. The swing is held aside so that the ropes make an angle of 46 o with the vertical. Use conservation of energy to determine the speed the child will have at the bottom of the arc when she is let go.

Answer 1

(M/2)Vmax^2 = M g L(1 - cos46)

L(1- cos 46) is the maximum rise of the swing above the bottom position, where the velocity is Vmax

Vmax = sqrt[2 g L (1-cos46)]

Answer 2

does 1-cos46 represent L or is L part of that equation?

Answer 3

L is the rope length, and is part of the equation. I already told you what
L*(1- cos 46) is .