Mechanical energy of a pendulum- I just can't get it!! 1. The problem statement, all variables and given/known data A pendulum of length 140 cm swings with an amplitude of 1.9 cm. Its mechanical energy is 5.7 mJ. What is the mechanical energy of the same pendulum when it swings with an amplitude of 3.7 cm? 2. Relevant equations ME = PE + KE PE = 1/2 k x^2 PE = mgh KE = 1/2 m v^2 and I also know that at the top of the arc (amplitude) all of the energy is PE 3. The attempt at a solution I keep trying to solve this and always end up with 11.1 mJ - this answer is wrong! I don't know what else to do.