Answer:
m g h = 1/2 m v^2 potential energy will be converted to kinetic energy
h = h0 (1 - cos theta) where theta is the displacement
theta = 30 / 50 = .6 theta = 36.9 deg
v^2 = 2 g h from above
h = 50 (1 - cos 36.9) = 50 * .2 = 10 cm
v = (2 * 980 * 10)^12 = 140 cm/sec
