# Homework Help: Need help with homework

1. Jan 18, 2005

### sbpatel

A 150-kg merry go round in the shape of a horizontal disk with a radius of 1.50m is set in motion by wrapping a rope about the rim of the disk and pulling on the rope. What constant force would have to be exerted on the rope to bring the merry-go-round from rest to an angular speed of .500 rev/s in 2.00s.

2. Jan 18, 2005

### MathStudent

hint:
what is the inertia of a disk?
what angular acceleration is required to bring the m-g-r to that speed in that given time?
Use newton's second law relating Torque to inertia and angular acceleration.
Use rotational kinematics equations to solve for angular acceleration and speed ( don't forget to convert the rev/s to radians/s before using these equations... you'll have to convert back to rev/s once you get the answer)

Show any work you've gotten so far and we'll add assistance.

Last edited: Jan 18, 2005
3. Jan 18, 2005

### sbpatel

well i really have no clue how to do this problem. My physics teacher genius is a but he does not know how to teach. Could someone please show me how to do it?

4. Jan 18, 2005

### Parth Dave

MathStudent just told you exactly what you have to do. It's up to you to do it. Give it a try and see how it goes. If you still can't figure it out, then come back and show us what you did.