A particle is thrown at time `t=0` with a velocity of 10 m/s at an angle of `60^(@)` with the horizontal from a point on an incline plane, making an angle of `30^(@)` with the horizontal. The time when the velocity of the projectile becomes parallel to the incline is :

Options

A. `(2)/(sqrt3) sec`
B. `(1)/(sqrt3) sec`
C. `sqrt3 sec`
D. `(1)/(2 sqrt3) sec`

Answer

B

Explanation

`v_(y) = v sin 30^(@) - g cos 30^(@) t`
`t = (v sin 30^(@))/(g cos 30^(@)) = (v)/(g) (1)/(sqrt3) = (1)/(sqrt3) sec`