Question

A rock falls from a vertical cliff that is 4.0 m tall and experiences no significant air resistance as it falls. At what speed will its gravitational potential energy (relative to the base of the cliff) be equal to its kinetic energy

Answer 1

Answer:

About 6.26m/s

Explanation:

$mgh=\dfrac{1}{2}mv^2$

Divide both sides by mass:

$gh=\dfrac{1}{2}v^2$

Since the point of equality of kinetic and potential energy will be halfway down the cliff, height will be 4/2=2 meters.

$(9.8)(2)=\dfrac{1}{2}v^2 \\\\v^2=39.4 \\\\v\approx 6.26m/s$

Hope this helps!