Question

An object is dropped from a 15 m ledge.how fast it is moving just before it hits the ground

Answer 1

Height from which an object is dropped = 15 m

The motion is happening under gravity.

Hence, the acceleration due to gravity = 9.8 $\frac{m}{s^2}\)$

Since, the object is dropped. Hence, its initial velocity = 0

Let the final velocity be v.

Now, using third equation of motion:

$v_f^2 = v_i^2 + 2 \times a \times H$

$\(v_f^2 = 0^2 + 2 \times 9.8 \times 15\)$

$\(v_f^2 = 294\)$

$\(v_f = 17.14 \frac{m}{s}\)$

Hence, the final speed just before hitting the ground is 17.14 m/s.