# Bullet fired in a pendulum. Calculate the initial speed of the bullet.

I've been trying to figure this out for a while and it's due tomorrow...any help would be greatly appreciated.

A .005 kg bullet is fired into a 4.0 kg pendulum bob initially at rest and becomes embedded in it. If the pendulum rises a vertical distance of 5.0 cm, calculate the initial speed of the bullet.

I tried to use a kinematics equation to find the velocity, but I needed an acceleration, so I tried to use F=ma, but I'm retarded or something but couldn't figure it out any way. Thanks for any help offered.

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ZapperZ
Staff Emeritus
febreze said:
I've been trying to figure this out for a while and it's due tomorrow...any help would be greatly appreciated.
A .005 kg bullet is fired into a 4.0 kg pendulum bob initially at rest and becomes embedded in it. If the pendulum rises a vertical distance of 5.0 cm, calculate the initial speed of the bullet.
I tried to use a kinematics equation to find the velocity, but I needed an acceleration, so I tried to use F=ma, but I'm retarded or something but couldn't figure it out any way. Thanks for any help offered.
1. Use conservation of momentum when the bullet hits the pendulum.

2. Then use conservation of energy when the bullet+pendulum swing to the top.

Zz.