Two seconds after projection a projectile is travelling in a direction inclined at 30∘ to the horizontal after one more sec, it is travelling horizontally, the magnitude and direction of its velocity are
20√3m/sec,60∘
Let in 2 sec body reaches upto point A and after one more sec upto point B.
Total time of ascent for a body is given 3 sec i.e. t=u sin θg=3
∴ u sin θ=10×3=30 .............(i)
Horizontal component of velocity remains always constant
u cos θ=vcos30∘ ..........(ii)
For vertical upward motion between point O and A
v sin 30∘=u sin θ−g×2 [Using v=u−gtv sin 30∘=30−20 [As u sin θ=30]
Substituting this value in equation (ii) u coa θ=20 cos 30∘=10√3......(iii)
From equation (i) and (iii) u=20√3and θ=60∘