What is the Tension in a String Holding a Ball in Motion?

[codz30]

Homework Statement

A ball of mass m on the end of a string is released from rest when the string is held horizontal
eg:
0-----

Prove that as the ball moves through the lowest point in its swing the string has a magnitude equal to three times the weight of the ball.

Homework Equations

Fc = mv^2/r
Weight = mg

The Attempt at a Solution

Because its motion in a vertical circular plane, I thought that mv^2/r would be needed, obviously the equation would end up something like
xxxxxx = 3mg
But I'm not sure how or why that would happen?
Any thoughts?

 

[LowlyPion]

Welcome to PF.

Consider what the kinetic energy is of the ball at the lowest point.

Using your knowledge of centripetal acceleration and the weight then what is the force on the string at that point?

 

[Dr.D]

What does it mean to say, "...the string has a magnitude equal to three times the weight of the ball"? How does the string have a magnitude?

 

[LowlyPion]

What does it mean to say, "...the string has a magnitude equal to three times the weight of the ball"? How does the string have a magnitude?

I'm sure they intend the "tension in the string" ...

 

[Dr.D]

The point is, it would really help if people asking questions would learn to ask those questions.