A particle is projected vertically upwards with a speed of `16ms^-1`. After some time, when it again passes through the point of projection, its speed is found to be `8ms^-1`. It is known that the work done by air resistance is same during upward and downward motion. Then the maximum height attained by the particle is (take `g=10ms^-2`)

Options

A. (a) `8m`
B. (b) `4.8m`
C. (c) `17.6m`
D. (d) `12.8m`

Answer

A

Explanation

From work-energy theorem, for upward motion
`1/2m(16)^2=mgh+W` (work done by air resistance)
for downward motion,
`1/2m(8)^2=mgh-Wimplies1/2[(16)^2+(8)^2]=2gh`
or `h=8m`