Physics question?

Question

A simple pendulum, 2.0m in length, is released with a push when the support string is at an angle of 25° from vertical. if the intial speed of the suspensed mass is 1.2 m/s when at the release point, what is its speed at the bottom of the swing?

Answer 1

The total energy of the pendulum at the instant of launch is

1/2 m v^2 + m g h

where v is 1.2 m/s
h is the height above the bottom

h = L - L cos 25 degrees

The total energy of the pendulum at the bottom of the arc is

1/2 m vb ^ 2

Set these two expressions equal and solve for vb. Note that you don't know the mass, but it doesn't matter; it cancels from every term.