Question

An object is dropped from rest at a height of 300m. Find: a.) its velocity

after 2 sec. b.) the time it takes for the object to reach the ground c.) what velocity does it

hit the ground?

Answer 1

a) $v=gt=9.81\cdot2=19.62\ (m/s)$

b) $s=gt^2/2\to t=\sqrt{\frac{2s}{g}}=\sqrt{\frac{2\cdot 300}{9.81}}=7.82\ (s)$

c) $mgh=mv^2/2\to v=\sqrt{2gh}=\sqrt{2\cdot9.81\cdot300}=76.72\ (m/s)$