P is a point moving with constant speed `10 m//s` such that is velocity vector always maintains an angle `60^(@)` with line OP as shown in figure (O is a fixed point in space). The initial distance between O and P is 100 m.

Options

A. `10 sec`
B. `15 sec`
C. `20 sec`
D. `20sqrt(3) sec`

Answer

C

Explanation

Velocity of approach of P and O is
`-(dx)/(dt) =v cos 60^(@) =5 m//s`
It can be seen that velocity of approach is always constant.
`:.` P reaches O after =`100/5` =20 sec.