# Rotation and Angular Momentum: Solving for thrust of a rocket

by engineer08
Tags: angular, momentum, rocket, rotation, solving, thrust
 P: 4 1. A solid bar of length L = 0.5m and with W = 0.1m weighs 2kg. It also has two constant-thrust rockets attached on either end. Each rocket is small enough to be considered a point mass of 0.25kg. If the bar is initially at rest and in two seconds after the rockets are fired it achieves a rotation rate of 1000rpm, determine the thrust of each rocket. 2. Relevant equations torque = I * angular acceleration I = (1/12)*(L^2+W^2)*M 3. I found I, angular momentum, to be 0.0542. I am not sure what to do from there.
 HW Helper P: 2,156 I is moment of inertia, not angular momentum. What equation do you know that relates torque and angular momentum (which is usually written L)?
 P: 4 Correct my apology, I is moment of inertia. An equation I know that relates torque with angular momentum 'L' is: torque = dL/dt = d(Iw)/dt The acceleration changed from 0 to 1000rpm in 2 seconds. and L=Iw, which is the angular velocity times the moment of inertia. I'm confused as to what to do
HW Helper
P: 2,156

## Rotation and Angular Momentum: Solving for thrust of a rocket

It's not acceleration that changed from 0 to 1000rpm in 2 seconds