A pendulum consists of a 4.0 kg stone swinging on a 3.2 m string of negligible mass. The stone has a speed of 7.7 m/s when it passes its lowest point.
(a) What is the speed when the string is at 62° to the vertical?
(b) What is the greatest angle with the vertical that the string will reach during the stone's motion?
(c) If the potential energy of the pendulum-Earth system is taken to be zero at the stone's lowest point, what is the total mechanical energy of the system?
The Attempt at a Solution
I'm all confused >.< I figured there wold be max KE in the middle. Then there would be some KE & PE at the 62 degree part.. but idn what to do.. ugh I tried Ei = Ef so then Ei = .5mv2 but what would Ef be... idn.. i was thinking about centripetal force... idn i'm hopeless >.<