Question

A particle is projected from ground for maximum range 80m. Time of flight for this projectile is?

Answer 1

The maximum range of this projectile is 80 m:

R = 80 m

R = u² sin (2 · 45°) / g ,    because the maximum range is with the initial angle of 45°.

80 = u² sin 90° / g   ( we will use g = 10 m/s² )

u² = 80 g = 800

u = √ 800 = 28.28 m/s

Also R = ux · t   and ux = u · cos 45° = 28.28 · 0.77 = 20 m/s

80 m = 20 m/s · t

t = 80 m : 20 m/s = 4 s

Answer: Time of flight of this projectile is 4 seconds.