Question

A rock falls from a cliff. What is its velocity after 4 seconds, in m/s?

Answer 1

The velocity of the rock will be $-39.24\frac{m}{s}$

Why?

Please note that the sign of the result, will depend on where we assume the origin, for this problem, I'll assume that the origin is located at the ground, so the velocity will be negative.

To calculate the speed of the rock, we need to use the following formula:

$v_{4seconds}=v_{o}-g*t\\\\v_{4seconds}=v_{o}-(9.81\frac{m}{s^{2}})*(4seconds)\\\\v_{4seconds}=0-(9.81\frac{m}{s^{2}})*(4seconds)=-39.24\frac{m}{s}$

Hence, we have that the velocity of the rock will be $-39.24\frac{m}{s}$

Have a nice day!