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

Question

Quizplus · Accepted Answer

The magnitude of the velocity of the rock can be found using the Pythagorean theorem, combining the horizontal velocity (which remains constant at 20 m/s due to no horizontal forces) and the vertical velocity (which increases due to gravity, $9.8 m/s^2$). After 2.0 s, the vertical velocity is $9.8 m/s^2 \times 2.0 s = 19.6 m/s$. The magnitude of the total velocity is $\sqrt{(20^2 + 19.6^2)} \approx 28 m/s$.

You Throw a Rock Horizontally Off a Cliff with a Speed