If retardation produced by air resistances to projectile is one-tenth of acceleration due to gravity, the time to reach maximum height approximately-

Options

A. Decreases by 11 percent
B. Increases by 11 percent
C. Decreases by 9 percent
D. Increases by 9 percent

Answer

C

Explanation

Without air resistance.
`I_(0) = (u sin alpha)/g`…… (i)
with air resistance.
`t_(1) = (u sin alpha)/(g + a) = (u sin alpha)/(g + g/10) = (10/11) (u sin alpha)/g`….. (ii)
`t_(1) = 10/11 t_(0) rArr t_(0) - t_(1) = 1/11 t_(0) = 0.09 t_(0)`
`rArrr (t_(0) - t_(1))/t_(0) = 0.09`