Circular Motion - Finding Tension

[swede5670]

Homework Statement

A ball on the end of a string is cleverly revolved at a uniform rate in a vertical circle of radius 65.0 cm, as shown in Fig. 5-33. Its speed is 4.00 m/s and its mass is 0.300 kg.
(a) Calculate the tension in the string when the ball is at the top of its path.
(b) Calculate the tension in the string when the ball is at the bottom of its path.

Homework Equations

Fnet=ma
v^2/r=a

The Attempt at a Solution

This is for my quiz review packet which is unfortunately due tomorrow, and I'm confused about how to solve this problem.
I'm thinking that since this problem involves tension I'm going to need the equation Fnet=ma.
To find A first I take the velocity 4m/s and put it to the power of 2, so its (16m/s)/radius= centripetal acceleration)
In this case 16/.65=a so 24.62m/s is the acceleration
Fnet at the top of the circle is mg+t (.300)(9.81)+t
2.94300+X=.300*24.62
2.94300+x=7.38600
4.44300=x

If this is right I know how to do the second part.

 

[Morhas]

To start, draw a free body diagram of both situations to see all the forces acting on the objects and how they're acting. Then come up with a Fnet statement, by looking at all the forces.

 

[rl.bhat]

That is right.