Posted by Emily Grossman on .
How do you solve this problem?
A ball on the end of a string is revolved at a uniform rate in a vertical circle radius of 72.0 cm, as shown in figure. If its speed is 4.00m/s and its mass is .300 kg. Calculate the tension in the string when the ball is a) at the top of the path, and b). when it's at the bottom?

Physics 
drwls,
a) Mg + T = MV^2/R
T = M(V^2/R g)
b) T  Mg = MV^2/R
T = M(V^2/R + g)
T is the tension that you want to compute.
Make sure R is in meters when you do the calculation. The force will be in Newtons. 
Physics 
Emily Grossman,
Can you like work the problem out so i can see how it is done?

Physics 
Emily Grossman,
what is the V in this case? That's what throwing me off..

Physics 
bobpursley,
V is velocity, given as 4m/s

Physics 
Emily Grossman,
Okay, I worked them out, but I am not getting the answer they should be. Like a) i am getting as what should be the answer as b. So, i don't if someone could work them out or tell me maybe what doing wrong. Thanks!

Physics 
drwls,
If the answers to a and b answers are interchanged, your book may be wrong.
All you have to do is use the formulas provided, using these variables:
V = 4.0 m/s
M = 0.3 kg
g = 9.8 m/s^2
R = 0.72 m 
Physics 
Emily Grossman,
Okay, so for a) get 3.13 and b). get 16.5?