What is his potential energy (in kJ) when the angle between the swing and the vertical is 35 degrees?

A 50 kg boy is on a massless swing that has an effective length of 3.0 m. His potential energy is zero when the angle between the swing and the vertical is zero. What is his potential energy (in kJ) when the angle between the swing and the vertical is 35 degrees?|||Draw yourself a picture to see how the trigonometry works so that the boy's height above the low point, h, is l (1-cos angle).





potential energy = mgh





= mgl (1-cos angle)





They give you m, l, and the angle. You know g. Plugnchug. Don't forget to multiply by k/1000 to get to kJ.|||mgL(1 - cos(伪)) = 2 mgL sin虏(伪/2)