Question

a student drops a rock from the top of a bridge. how fast is the rock moving after falling for 3 seconds? assume that the rock does not hit top ground in 3 seconds. resistance is negligible. a 10 m/s b 30 m/s c 60 m/s d 90 m/s

Explanation:

Step1: Identify the kinematic - equation

We use the equation $v = v_0+at$. Since the rock is dropped, $v_0 = 0\ m/s$, and the acceleration $a = g= 10\ m/s^{2}$ (approximate value of gravitational acceleration on Earth), and $t = 3\ s$.

Step2: Substitute values into the equation

$v=0 + 10\times3$.
$v = 30\ m/s$.

Answer:

C. 30 m/s