A projectile is projected at `10ms^(-1)` by making an angle `60^(@)` to the horizontal. After sometime, its velocity makes an angle of `30^(@)` to the horzontal . Its speed at this instant is:

Options

A. `(10)/sqrt(3)`
B. `10sqrt(3)`
C. `(5)/sqrt(3)`
D. `5sqrt(3)`

Answer

a

Explanation

Let u and v be the initial velocity and velocity at the instant when projectle makes an angle `30^(@)` with the horzontal.

As horizontal velocity remains unifrom, therefore.
`v cos 30^(@)=u cos 60^(@)`
`v((sqrt(3))/(2))=10xx(1)/(2)`
`v=(10)/sqrt(3)ms^(-1)`