Question

A 10.kg lead brick falls from a height of 2.0m. Find the momentum as it reaches the ground.

Answer 1

Use the following energy relations
$E_{Grav}=mgh$
$E _{Kinetic} = \frac{1}{2}m v^{2}$
Then look at momentum put into the kinetic energy formula.  Recall
$p=mv$
Now we see that
$E _{Kinetic}= \frac{ p^{2} }{2m}$
Since the kinetic energy at the end of the fall is the same as the potential (Gravitational) energy at the beginning we set them equal
$mgh= \frac{ p^{2} }{2m}$
$m\sqrt{2gh} = p=62.61 \frac{kgm}{s}$