The ballistic pendulum (see the figure below) is a device used to measure the speed of a fast-moving projectile such as a bullet. The bullet is fired into a large block of wood suspended from some light wires. The bullet is stopped by the block, and the entire system swings up to a height h. In figure a, a bullet and a wooden block are shown in two configurations. In the first configuration, the block, labeled m2, hangs vertically from a ceiling. A bullet, labeled m1, approaches the block horizontally from the left. A rightward arrow points from the bullet and is labeled vector v1i. A rightward arrow, shorter than the first, points from the block and is labeled vector vsys. In the second configuration, the bullet is embedded in the block, and the block has swung up and to the right, a vertical distance h from its initial position. The block and bullet are labeled m1 + m2. In figure b, a photograph shows a laboratory ballistic pendulum. A person pulls a trigger on the left, and a pendulum is shown in multiple positions as it swings up and to the right.
(a) Determine the ratio of the momentum immediately after the collision to the momentum immediately before the collision. pf/pi =