Question

a ball is dropped from an unknown height. it takes 3.0s to reach the ground. how fast is it going when it reaches the ground? 0m/s 10m/s 30m/s 45m/s

Explanation:

Step1: Identify the kinematic - equation

We use the equation $v = v_0+at$. For a dropped object, the initial velocity $v_0 = 0\ m/s$, and the acceleration $a = g= 10\ m/s^{2}$ (approximate value of gravitational acceleration near the Earth's surface), and the time $t = 3.0\ s$.

Step2: Substitute the values

Substitute $v_0 = 0\ m/s$, $a = 10\ m/s^{2}$, and $t = 3.0\ s$ into the equation $v = v_0+at$. We get $v=0 + 10\times3$.

Step3: Calculate the final velocity

$v=30\ m/s$.

Answer:

C. 30m/s