@Arvind gupta
For Q
U=0,
So
Now for P
if the angle of projection of P with the incline surface is α
=> ucosα = speed along the plane, a = gsinθ° = acceleration along the plane
Similarly usinα = speed perpendicular to the plane, a = gcosθ° = acceleration perpendicular to the plane
time of flight (For P) = 2usinα/gcosθ° = 4 s
usinα = 2gcosθ°
distance travelled down incline = s = ut + ½at²
Sp= 4ucosα + 8gsinθ°
So Sp=Sq
= 4ucosα + 8gsinθ° = 8gsinθ°
=> cosα = 0 or α = 90°
So we get u = 2gcosθ°=