You throw a rock horizontally off a cliff with a speed of 20 m/s and no significant air resistance. After 2.0 s, the magnitude of the velocity of the rock is closest to
A) 28 m/s
B) 37 m/s
C) 20 m/s
D) 40 m/s

Question

Quizplus · Accepted Answer

The magnitude of the velocity of the rock can be found using the Pythagorean theorem, combining the horizontal and vertical components of velocity. The horizontal velocity remains constant at 20 m/s (since there's no air resistance). The vertical velocity can be found using $v = gt$, where $g = 9.8 \, \text{m/s}^2$ is the acceleration due to gravity and $t = 2.0 \, \text{s}$ is the time. So, $v = 9.8 \times 2.0 = 19.6 \, \text{m/s}$. The magnitude of the total velocity is $\sqrt{20^2 + 19.6^2} \approx 28 \, \text{m/s}$.

You Throw a Rock Horizontally Off a Cliff with a Speed