A pendulum of length 150cm swings with an amplitude of 1.8cm. Its mechanical energy is 6mJ. What is the mechanical energy of the same pendulum when it swings with an amplitude of 4.3cm? The answer is supposed to be in mJ. How do I relate the mechanical energy to what they gave me in the problem. I found the angular velocity, but did I need to do that? Is there an equation that relates energy with amplitude? Thanks.