Suppose a pendulum bob is swinging back and forth. If the highest point is 12.5 cm above the lowest point, what would be speed of the bob in m/s when it passes the lowest point (no friction or air resistance)? Think Conservation of Mechanical Energy.

The speed of the bob  when it passes the lowest point  

Explanation:

Given data

When a pendulum swinging back & forth then at highest point the velocity is zero and lowest point velocity is maximum.

Velocity at lowest point is given by  

Therefore the speed of the bob  when it passes the lowest point

real, smaller and upside-down.   so the answer should be b.