Chapter 8.7, Problem 1CFU

To determine

To Find: The situations in which the projectile travels vertically and find the angle with the horizontal at which the projectile must be launched.

Answer to Problem 1CFU

Theprojectile must be at the angle of $90°$ .

Explanation of Solution

Consider the situation in which the projectile travels vertically is the situation when the stone is thrown perpendicularly towards the sky and the projectile travels vertically.

Then, the horizontal component is zero that is,

  $\begin{array}{l}\cos \theta =\left|\frac{\overline{v_x}}{v}\right|\\ \cos \theta =0\\ \theta =90°\end{array}$

Thus, the projectile must be at the angle of $90°$