Answer
Formula
Range of a projectile motion is given by:
R = sin(2θ) / g
- R is the range of projectile
- θ is the angle at which it is projected
- U is initial velocity
- g is gravitational acceleration
So, we can say the range is directly proportional to sin(2θ)
R ∝ sin(2θ)
Method-1
Using direct values of sin(2 x 30) , sin(2 x 40), sin(2 x 55) and sin(2 x 65)
sin (60) = 0.866
sin (80) = 0.98
sin (110) = 0.93
sin (130) = 0.76
So, The horizontal range will be largest for the one projected at an angle 40°
Method-2
Without using direct values
Concept to be used-
Range projected at angle θ and at angle 90-θ will be same.
So, we can say that range of the body projected at 55° will be equal to (90-55)° = 35°
Range of the body projected at 65° will be equal to (90-65)° = 25°
Since the range is directly proportional to twice of θ,
2 x 30° = 60°
2 x 40° = 80°
2 x 35° = 70°
2 x 25° = 50°
Value of sin x always increases from 0 to 90°
Maximum value of 2θ is 80°.
So, The horizontal range will be largest for the one projected at an angle 40°