A partile is projected up an incline (inclination angle `= 30^(@)`) with `15sqrt(3) m//s` at an angle of `30^(@)` with the incline (as shown in figure) `(g = 10 m//s^(2))`

Options

A. `1.5` sec later, angle between acceleration & velocity is `120^(@)`
B. `1.5` sec later, angle between acceleration & velocity is `60^(@)`.
C. Range on the incline is `45 m`
D. Time of flight on the incline is `3` sec.

Answer

A, C, D

Explanation

For motion `bot` to incline `0 = (u sin 30^(@))t - (1)/(2) (g cos 30^(@))"lt"^(2)`
`rArr t = (2usin30^(@))/(gcos30^(@)) = 3 sec =` Time of flight
`rArr` at `1.5 sec`, velocity is parallel to incline
`rArr` angle between velocity & acceleration is `120^(@)`

for motion parallel to incline
`R = (u cos 30^(@))t - (1)/(2)(g sin 30^(@))t^(2)` & `t = 3 sec`
`rArr R = 45 m`