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

Options

A. decreases by 11 percent
B. increases by 11 percent
C. decreases by 9 percent
D. increases by 9 percent

Answer

C

Explanation

Here let .a be retardation in addition to .g. . Total retardation is `a_(R )=a+g` where `a=g/10`
`:.`Time of Flight `T=(usintheta)/(g+a)`
Now `T=(usintheta)/(11g//10)=(10usintheta)/(11g)`
Let t be the time of flight when only "g" is acting, then
`t=(usintheta)/g` or `T=10/11xxt`
% of decrease=`(t-T)/txx100`
`=(t-10/11t)/t xx100=100/11=9.1%approx`9%