# Homework Help: Momentum and Energy problem, conservation.?

1. Mar 17, 2013

### student1234

1. The problem statement, all variables and given/known data

A pendulum of 9.99 kg is initially at rest, just skimming the floor below. A bullet of mass 0.01kg is fired at the bob. The bullet collides with the bob and embeds itself, after which the pendulum begins to move. The bullet-bob pendulum reaches the maximum vertical displacement of 4.60 cm.

a) Calculate the velocity of the bullet just before the impact with the bob. (ANS: 949m/s)

b) If a rubber bullet of mass 0.01kg was fired at the 9.99 bob with a speed of 949 m/s, and collided elastically with the bob, how high would the pendulum now rise?

ANS b: 18.4 cm

2. Relevant equations

P1 = P2 and E1 = E2

3. The attempt at a solution

a) I think we are supposed to use the conservation of momentum and energy to answer this but I cannot do it.

26 minutes ago - 4 days left to answer.

Last edited by a moderator: Mar 17, 2013
2. Mar 17, 2013

### vela

Staff Emeritus
You're right. You need to use conservation of momentum and energy. Show us your attempt at applying those principles.