A .150 kg ball is swung in a vertical circle on the end of a string that is 2.2 meters long. Determine the minimum speed the ball must have at the top of the arc so that it continues moving in a circle. Also calculate the tension in the string at the bottom of the swing assuming the ball is moving twice as fast as at the top. Finally, calculate the tangential velocity of the ball at the bottom of the swing.

-I've tried this question over many times and couldn't find the right formula to work out the problem...please help!

Thanks in Advance,

-Genxi
This is a question my teacher has written, I'm sorry if it doesn't make sense...