UPSEE Solved Model Paper 7

Given:
Speed of the cannon, u = 240 m/s
The cannon fires a projectile which hits the target located 5.1 km away at the same level. Thus, from projectile motion, we have the range as:
R = 5.1 km =

u2sin(2θ)

g

⇒ sin (2θ) =

5100m×9.8m∕s2

(240m∕s)2

= 0.88
⇒ 2θ = 60° or θ = 30°
The time period of a projectile is given as
T =

2usinθ

g

⇒ T =

2×240m∕s×sin30°

9.8m∕s2

=

2×240m∕s×0.5

9.8m∕s2

⇒ T = 24.5 s
Hence, option 'A' is correct.