Posted by Angelina on .
A 0.700kg ball is on the end of a rope that is 0.90 m in length. The ball and rope are attached to a pole and the entire apparatus, including the pole, rotates about the pole's symmetry axis. The rope makes an angle of 70.0° with respect to the vertical as shown. What is the tangential speed of the ball?

physics 
Angelina,
I was thinking that it would be .90tan(70)=2.47 m/s^2 but I am wrong so I don't know how to do this...

physics 
drwls,
Let the rope tension be T.
T sin70 = M V^2/R
T cos70 = M g
Now, divide the first equation by the second one.
tan70 = V^2/(R*g)
V^2 = (0.90)(9.8)(2.747)= 24.23 m^2/s^2
V = 4.92 m/s
Your answer does not have the dimensions of velocity, and must depend upon g. 
physics 
Angelina,
What is the tangential speed of the ball?
thnks but i tried both 24.23m^2/s^2 and 4.92 n neither are right i don't understand whats wrong 
physics 
Jim,
Radius should be 0.90Sin(70) that would account for the length of the path that the stone is traveling in. Use the equation above and substitute .90Sin(70) for the radius.