A projectile is thrown in the upward direction making an angle of 60^ with the horizontal direction with a velocity of 147 ~ms ⁻¹ . Then the time after which its inclination with the horizontal is 45^ , is

Step-by-step solution

Key Idea : At the two points of the trajectory during projection, the horizontal component of the velocity is the same. Horizontal component of velocity at angle 60^ = Horizontal component of velocity at 45^ i e, u 60^ =v 45^ or 147 1 2 =v 1 2 or v= 147 2 ~m / s Vertical component of u=u 60^ = 147 3 2 ~m Vertical component of v=v 45^ = 147 2 1 2 = 147 2 ~m but v_y=u_y+a t 147 2 = 147 3 2 -9.8 t or 9.8 t= 147 2 ( 3 -1) t=5.49 ~s