Question

The launching speed of a certain projectile is five times the speed it has at its maximum height. Its angle of projection is

• A. $\theta ={\cos }^{-1}\left(0.2\right)$
• B. $\theta ={\tan }^{-1}\left(0.2\right)$
• C. $\theta ={\sin }^{-1}\left(0.2\right)$
• D. $\theta =0^o$

Answer 1

The correct option is A $\theta ={\cos }^{-1}\left(0.2\right)$

At the maximum height,

The vertical component of the velocity is zero.

$u_y=usin\theta =0m/s$

The horizontal component of the velocity,

$u_x=ucos\theta$

$u=5ucos\theta$

$cos\theta =\frac{1}{5}=0.2$

$\theta =co{s}^{-1}\left(0.2\right)$

The correct option is A.