A 600g ball swings in a vertical circle at the end of a 1.2-m-long string. When the ball is at the bottom of the circle, the tension in the string is 18N. What is the speed at this point ?

Question

anonymous · Answer

Where did you get that from Yahoo? Ashley, this is a centripetal force question, as you only have m,v,r and F involved. The centripetal force acts TOWARDS the centre, and is provided by the Tension here. At the bottom of the circle, the weight is down and the tension up. Adding the forces (weight and tension), we are left with 12.114N of centripetal force. 

Now use $$F = \frac{ mv ^{2} }{ r }$$ to solve for v.