A child is swinging a swing. Minimum and maximum heights fo swing from the earth's surface are 0.75 m and 2 m respectively. The maximum velocity of this swing is

Options

A. 8 m/s
B. 10 m/s
C. 15 m/s
D. 5 m/s

Answer

D

Explanation

The height through which the child is lifted =2-0.75=1.25 m
At the lowest point it has maximum speed (v)
and its `K.E. =(1)/(2)mv^(2)`
and P.E. at the highest point =mgh
`(1)/(2)mv^(2)=mgh`
`therefore v=sqrt(2gh)=sqrt(2xx10xx1.25)=sqrt(25)=5m//s`