Question

A ball is thrown vertically upward with speed `10 m//s` and it returns to the ground with speed `8 m//s`. A constant air resistance acts. The minimum height attained by the ball is
A. 4.1 m
B. 5.1 m
C. 6.1 m
D. 7.1 m

Answer 1

Correct Answer - A

Upward motion `:(1)/(2)m(10)^2=mgh+Rh` .(i)
Downward motion: `mgh=(1)/(2)m(8)^2+Rh` .(ii)
From (i) and (ii), we get
`2mgh=(1)/(2)m(10)^2+(1)/(2)m(8)^2`
`h=((10)^2+(8)^2)/(4g)=(164)/(40)=4.1m`