# Simple physics math help

What is the tension in the string?

okay i have figured this much out,

Tsin(16.69) = m (v^2)/ r
T cos 16.69 -mg =0

i dont know how to solve for T though. i know it should be simple math, but i cant figure it out!

i have tried this

r(tsin 16.69) / v^2 = m
and Tcos16.69 / g = m

and then make them equal,

Tcos16.69 / g = r(Tsin16.69)/V^2

but now i am lost

## Answers and Replies

Doc Al
Mentor
What is the tension in the string?

okay i have figured this much out,

Tsin(16.69) = m (v^2)/ r
T cos 16.69 -mg =0
What are the knowns and unknowns?

cristo
Staff Emeritus
Science Advisor
What values out of those you have written down do you know? At the moment you have two equations in four unknowns, so you will not be able to solve them!

oh sorry! i know that r=.3 and m =.2

but i just realized that if i know those, i can just plug them into the 2nd equation and find T...i think

Doc Al
Mentor
Tsin(16.69) = m (v^2)/ r
T cos 16.69 -mg =0
What I would do is immediately combine these equations to eliminate T and solve for v. Then you can plug in that answer for T.

(If you write the second equation as T cos 16.69 = mg, it might be easier to see how to combine them.)

^ooh i understand what you are saying. thank you!