Question

A projectile is thrown in upward direction angle 60 degree with the horizontal direction velocity of 147 metre per second then the time after which its inclination with horizontal is 45 degree is

Answer 1

 let after time t its inclination with horizontal is 45
   at this time Vy /Vx =tan45  or Vy =Vx 
    Vx remains constant =147cos60 =Vy 
    now using equation of motion for verticle direction 
   Vy=Uy-gt..........eq1
   Uy=147sin60 ,Uy=147cos60 
 putting in eq 1, 
    t=5.36 sec