# Determine the tension in the pendulum string

1. Aug 1, 2010

### Ry122

1. The problem statement, all variables and given/known data
The ball in this conical pendulum is moving at constant velocity.
The length of the string is 1m and the ball is 0.5kg.
Determine the tension in the string.

[PLAIN]http://img685.imageshack.us/img685/7868/pedns.png [Broken]

2. Relevant equations

3. The attempt at a solution
The force that the ball exerts on the string is the tension inside the string
and the ball experiences two different forces.
One is the force the ball experiences due to gravity and the other is the force it experiences
due to the circular motion that it's undergoing.
The resultant of these two forces will give the tension inside the string.
The force due to gravity can be calculated with F=m x a
But I'm unsure as to how the force on the ball due to the circular motion of the ball can be calculated.
Does anyone know how this can be done?

Last edited by a moderator: May 4, 2017
2. Aug 1, 2010

### graphene

Re: pendulum

What is the expression for centrifugal force in terms of velocity & radius ?

3. Aug 1, 2010

### Ry122

Re: pendulum

F = m x (v^2)/R
But R can't be determined because theta is unknown.

4. Aug 1, 2010

### graphene

Re: pendulum

You do not need the exact value of $$\theta$$.
Just write down the equations for a generic $$\theta$$ and you could figure out how to proceed.