Question

A wrecking ball is suspended from a 7.0-m-long cable that makes a 25 ? angle with the vertical. the ball is released and swings down. part a what is the ball's speed at the lowest point? what is the ball's speed at the lowest point? 7.2 m/s 5.1 m/s 3.6 m/s 2.5 m/s

Answer 1

The height of the ball when lifted is given by 7sin(25)=2.96
the gravitational energy is mgh, the kinetic is (1/2)mv².  We can set these equal since the pendulum doesn't lose much energy
mgh = (1/2)mv²
we can divide by m (since we don't have it anyways)
gh = v²/2
v=√(gh/2) = √(9.81*2.96/2)=3.8m/s.
Not exactly one of your choices, but the right one none the less