Question

A ballistic pendulum is a device used to measure the speed of projectiles. It consists of a block of wood that hangs from a string. When the projectile hits the block, it causes the block to move upwards. In most devices, we measure the angle that the rope moves. In this device, we will measure the height that rises to. The mass of the block of wood is 2.50-kg and the mass of the bullet is 0.0100-kg. The block swings to a maximum height of 0.650 m above the initial position. Find the initial speed of the bullet.

Answer 1

Answer:

u = 875 m/s

Explanation:

Let's ASSUME the bullet stays inside the block which is initially at rest.

Conservation of Energy after the collision

½(m + M)v² = (m + M)gh

v = √(2gh)

Conservation of momentum during the collision

m(u) + M(0) = (m + M)v

u = (m + M)v/m = (1 + M/m)√(2gh)

u = (1 + 2.50/0.0100)√(2(9.81)(0.650) = 875.425...