A child is on a swing whose 4.0 m long chains make a maximum angle of 30 deg with the vertical. What is the child's maximum speed?

Question

I've found problems relating to this but include mass or delta(x) in how far from stationary. This problem doesnt include mass. Help?

Answer 1

mgh = 1/2 mv^2
m cancels.
h = 4 - 4cos30 (draw the triangle, you'll see)