# Homework Help: Applications of Newtons Law Question 1

1. Oct 22, 2008

### noasherelol

1. The problem statement, all variables and given/known data
A hockey puck of mass m is attached to a string that passes through a hole in the center of a table. The Hockey Puck moves in a circle or radius r. Tied to the other end of the string, and hanging vertically beneath the table is Mass M.. Assuming the table top is perfectly smooth, what speed must the hockey puck have if the mass M is to remain at rest?

2. Relevant equations
F=mv^2/r

3. The attempt at a solution

The Sum of all forces on the axis = mv^2/r
r-vsin(theta)=mv^2/r

Im think im wrong with this

*I might have other questions to ask later, im really stuck on newtons laws in physics

2. Oct 22, 2008

### Epsillon

Alright so Fg = Fc

Mg= mv^2/r

You do not have any numbers for this??

3. Oct 22, 2008

### noasherelol

nope it never gave numbers, i think this is why im so confused with it

4. Oct 23, 2008

### heth

Look at it as an algebra question once you've set up the equations. Rearrange it so that the thing they're asking you for is on its own on the left hand side of the equation.

(You should be doing this anyway even if you have numbers to plug in. So this is like a question where you have numbers - but without putting the numbers in at the end.)