A projectile is launched at ground level an angle of 15 degrees above the horizontal and lands down range. What other projection angle for the same speed would produce the same down-range distance?
A) 45 degrees
B) 50 degrees
C) 90 degrees
D) 75 degrees
E) 30 degrees

Question

Quizplus · Accepted Answer

The range of a projectile launched at an angle $\theta$ with a given speed is the same as that of a projectile launched at an angle of $90 - \theta$ degrees with the same speed. Since the initial angle is 15 degrees, the complementary angle that gives the same range is $90 - 15 = 75$ degrees.

A Projectile Is Launched at Ground Level an Angle of 15