An object is projected with a velocity of 100 ms\(^{-1}\) from the ground level at an angle \(\theta\) to the vertical. If the total time of flight of the projectile is 10 s, calculate \theta. (g = 10 ms\(^{-2}\)).
A
0o
B
30o
C
45o
D
60o
E
90o
Verified Correct Answer: D.
Physical Principles & Numerical Solution
T = \(\frac{2u sin \theta}{g}\)
sin \theta = \(\frac{Tg}{2u}\)
sin \theta = \(\frac{10 \times 10}{2 \times 100}\) = 0.5
\theta = sin\(^{- 0.5}\) = 30º
\(\theta\)\(_{horizontal}\) = 30º
But \(\theta\)\(_{vertical}\) = 90º - 30º = 60º
Source: Myschool Past Questions Archive (Record #25001)