# Homework Help: Circular motion of steel block

1. Nov 15, 2004

### nat

:yuck: I've been trying to figure this out forever

A 500g steel block rotates on a steel table while attached to a 2.0 meter long massless rod. compressed air is fed through the rod is ejected from a nozzle on the back of the block, exerting a force of 3.5N. The nozzle is 70 degrees from the radial line. The block starts out at rest.

what is the blocks angular velocity after 10 revolutions?
what is the tesion in the rod after 10 revolutions?

I know mu kentic of steel on steel is .6 I've been running myself around in circles for this problem!!

I know I have to add all the vector components together but I'm new at this stuff I can identify the force of.... gravity*mass thrust(but since it is connected at an angle I don't know how eactly to divide it into components), friction, I have no idea what the acceleration is.
I can do the circular motion that has a horizontal and verticle component, but the angle thing is throwing me!!

Last edited: Nov 16, 2004
2. Nov 16, 2004

### rayveldkamp

I haven't done a unit in dynamics since last semester so im a bit rusty...but i remember getting a problem similar to that, where i used the normal-tangential coordinate system for the block's acceleration and velocity (looking down on the table), and then analysed the friction and gravitational force with x-y coordinates (looking side on at the table).
Don't know if that helps, as i said its been a while.