Ballistic Pendulum Rifle: Solving for Post-Collision Height

[Tohte]

The problem:

https://tycho-s.phys.washington.edu/cgi/courses/shell/common/showme.pl?courses/phys121/autumn08/homework/06/IE_algebra_ballistic_pendulum_MOM/pic.gif

A rifle bullet of mass m = 0.03 kg traveling at vb = 240 m/s collides with and embeds itself in a pendulum of mass M = 2.88 kg, initially at rest and suspended vertically by massless strings of length L = 2 m.

How high does the pendulum-bullet combination rise after the collision?

I don't know the process for solving this equation, so help would be appreciated.

 

[Borek]

Energy preservation. Kinetic gets converted into potential.

 

[Tohte]

Okay, so I need to use PE = mgh. I don't understand what I do with the velocity of the bullet and how to setup the problem, if I could get a little more guidance it would help me out

Thanks.

 

[Borek]

What is formula for kinetic energy?

 

[shutoutsteve]

We did this the other day, except we just manipulated the formulas instead of working with actual values.
I am going to attempt to make sense of what I have for that note, so you may hear from me soon...

 

[Tohte]

What is formula for kinetic energy?

KE = (1/2)mv²

 

[Borek]

Is there something you still don't know? Just beware which mass is which - ballistic pendulum mass after hit is that of pendulum PLUS bullet.

 

[Tohte]

Is there something you still don't know? Just beware which mass is which - ballistic pendulum mass after hit is that of pendulum PLUS bullet.

I don't understand what it is I do with the equation for Kinetic Energy, I'm supposed to find the height of the bullet-pendulum system after the bullet hits the pendulum.

 

[Borek]

h as of mgh.

 

[Doc Al]

This problem is best solved in two stages:
(1) The collision itself. You need to find the speed of the block+bullet immediately after the collision. Hint: Energy is not conserved, but something else is.
(2) The rising of the pendulum after the collision. Here you do use energy conservation, as Borek explains.

 

[Borek]

Hint: Energy is not conserved, but something else is.

Do we have an emoticon for selffishslapping?