This is a simulation of a ballistic pendulum. A ballistic pendulum is a device used to determine the speed of a bullet.
Use the horizontal sliders to adjust the mass of the bullet, mass of the wood block, and the initial velocity of the bullet. Press the "Fire" button. The bullet collides with and sticks inside of the wood block. After the collision the wood block and bullet swing upward (and then back and forth). Use the vertical slider on the right to move the reference line in order to determine the maximum height reached by the bottom of the block. Use the masses of the block and bullet, the maximum height reached, and the concepts of conservation of momentum and energy to calculate the initial velocity of the bullet. Use the checkbox to show the initial velocity once you have finished your calculation and see how close you came.