Question

The string in the figure is 50 cm long. When the ball is released from rest,it will swing along the dotted arc.how fast, in m/s, will it be going at the lowest point in its swing?​

Answer 1

P E at upper point =mgr

= m × 10 × 50/100

P E = 5m

K E at lowest point = mv^2/2

E V = P E + K E = mv^2/2= 0

using conservation of energy

mv^2/2 =5m

v^2 =10

v =√10m/s

=3.1m/s