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. 8 m
B. `4.8 m`
C. `17.6 m`
D. `12.8 m`

Answer

A

Explanation

From work energy theorem
for upward motion
`(1)/(2)m(16)_(2)=mgh +W` (work by air resistance) for downward motion
`(1)/(2)m(8)_(2)=mgh -W`
`(1)/(2)[(16)_(2)+(8)_(2)] =3gh` or `h = 8m`