Question

The bob of a single pendulum is imparted a velocity of 5ms -1 when it is at its mean position. To what maximum vertical height will it rise on reaching at its extreme position if 60% of its energy is lost in overcoming the friction of air (Take g= 10 ms-2)​

Answer 1

When it is at mean position it will have a K.E of 0.5mv

2

.

K.E=0.5×m×5×5=12.5×m J

60 % of this K.E is lost hence remaining is equal to (40/100)12.5×m=5m

P.E=mgh=5×m

h=5/g=5/10=0.5m

Hence it goes to a height of 0.5m.