Question

A 0.70 kg teddy bear is nudged off a window sill and falls 3.35 m to the ground. what is its kinetic energy at the instant it hits the ground?

Answer 1

This question can be solved by using kinetic-potential energy postulate. It states that for any point sum of potential and kinetic energy of a body is same.

$E_{sum} = E_{kinetic}+ E_{potential}$

At the given height potential energy is:
$E_{potential} =m*g*h \\ E_{potential} =0.70*3.35*9.81 \\ E_{potential} =23J$

When the body reaches ground height is 0m and the potential energy is 0J. This means that all potential energy is transformed into kinetic energy.
$E_{kinetic} =23J$

At the moment when body hits the ground the kinetic energy is 23J.