Question

A body of mass 5 kg, projected at an angle of 45° from the ground covers a horizontal range of 45 m, acceleration due to gravity is g = 10 m/s^2, what is the velocity with which it was projected covered?

(a) 21.21 m/s

(b) 20 m/s

(c) 22 m/s

(d) 21.1 m/s

The question was asked in a national level competition.

My doubt stems from Simple Projectile Motion topic in portion Motion in a Plane of Physics – Class 11

Answer 1

Correct answer is (a) 21.21 m/s

The best I can explain: The formula for horizontal range is R = v^2 (sin 2θ)/g. Here, R = 45, θ = 45°, g = 10. Hence, on solving we will get velocity as 21.21 m/s. The result can be cross checked by putting this value of velocity and finding out the range.