Ballistic Pendulum: Find the Bullet's Speed

[chawki]

Homework Statement

The ballistic pendulum is a block of 3.0 kg mass suspended from a thread 2.5 m long. A bullet with a mass of 9.0 g hits the block and sticks in it, the result being a deflection of the system by an angle of 18^o.

Homework Equations

Find the bullet’s speed.

The Attempt at a Solution

all i know is t=2*pi*$$\sqrt{}(l/g)$$

 

[cupid.callin]

use conservation of momentum to find final speed

and then use energy conservation principle

 

[ashishsinghal]

all i know is t=2*pi*$$\sqrt{}(l/g)$$

This won't help!

I agree with cupid.callin