Part 2: Potato Gun Ballistic Pendulum - What's the Velocity? A clever way to measure the velocity of a very fast projectile (like a potato out of a potato gun) is to fire it into a more massive pendulum and measure the highest point in Potato = 0.145 kg the swing. Bucket . 25 kg Click Here for Video Step 1: Conservation of Energy Initial Final KE PE Ih Potato . Buch Use the conservation of energy and the maximum height of the bucket's swing to calculate the top velocity of the bucket and potato when it starts swinging after the collision. Step 2: Conservation of Momentum Initial Final Potato . Bucket Use the conservation of momentum and the velocity of the potato/bucket system from part 1 to calculate the initial velocity of the potato + my mv NO Pot Putt Bucket Buc Potato Velocity