Question

a rock falls off a cliff and hits the ground after three seconds. the rocks velocity is 29.4 m/s when it hits the ground. what is its acceleration of the rock in the downward direction? 0.31 $\frac{m}{s^{2}}$ 3 $\frac{m}{s^{2}}$ 9.8 $\frac{m}{s^{2}}$ 88.2 $\frac{m}{s^{2}}$

Explanation:

Step1: Recall acceleration formula

The formula for acceleration is $a=\frac{v - u}{t}$, where $a$ is acceleration, $v$ is final - velocity, $u$ is initial velocity, and $t$ is time. The rock starts from rest, so $u = 0\ m/s$, $v=29.4\ m/s$, and $t = 3\ s$.

Step2: Substitute values into formula

$a=\frac{29.4 - 0}{3}$
$a=\frac{29.4}{3}=9.8\ m/s^{2}$

Answer:

$9.8\ \frac{m}{s^{2}}$