Asked by Emily Grossman

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?
Answered by 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.
Answered by Emily Grossman
Can you like work the problem out so i can see how it is done?
Answered by Emily Grossman
what is the V in this case? That's what throwing me off..
Answered by bobpursley
V is velocity, given as 4m/s
Answered by 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!
Answered by 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
Answered by Emily Grossman
Okay, so for a) get 3.13 and b). get 16.5?
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