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 m/s² 3 m/s² 9.8 m/s² 88.2 m/s²

Explanation:

Step1: Recall acceleration formula

Acceleration $a=\frac{\Delta v}{\Delta t}$. The initial velocity $v_0 = 0$ m/s (starts from rest), final velocity $v = 29.4$ m/s and time $t=3$ s.

Step2: Calculate acceleration

$a=\frac{v - v_0}{t}=\frac{29.4- 0}{3}$$=\frac{29.4}{3}=9.8$ m/s²

Answer:

$9.8\frac{m}{s^2}$ (corresponds to the third - option)