Assume friction and air resistance are negligible during the swing so we can use conservation of mechanical energy to determine the speed of the pendulum + projectile immediately after the collision. ...Assume friction and air resistance are negligible during the swing so we can use conservation of mechanical energy to determine the speed of the pendulum + projectile immediately after the collision. Fire the projectile and measure the final height of the center of gravity of the pendulum. The final velocity of the collision is equal to the velocity at the start of the swing, which you found above.
