Angular velocity of a conical pendulum in rpm

kerbyjonsonjr

1. The problem statement, all variables and given/known data
A conical pendulum is formed by attaching a 0.900 kg ball to a 1.00 m long string, then allowing the mass to move in a horizontal circle of radius 20.0 cm . What is the ball's angular velocity, in rpm?


2. Relevant equations
v=[tex]\sqrt{}L*g*sin(\vartheta)*tan(\vartheta)[/tex]
w=v/r

3. The attempt at a solution
Since the radius is .2 m and the length of the string is 1m I used cos([tex]\vartheta) [/tex] and found [tex]\vartheta[/tex] to be 78.46 degrees. Then I used that equation for tangential velocity so I had v=[tex]\sqrt{}1*9.81*sin(78.46)*tan(78.46)[/tex] and got v=6.86 m/s so then I used w=v/r and got w=34.3 rad/sec which I then converted to rpm by multiplying 34.3 by 60 seconds times 1 rev/2[tex]\pi[/tex] and got 327.5 rpm and that is wrong. I don't know where I went wrong. I greatly appreciate any help.

hage567

I don't think you have the right angle. Double check how you got that.