Camron Higgins

2023-03-13

A rock of mass $m$ is dropped to the ground from a height $h$. A second rock with a mass of $2m$ is dropped from the same height. When the second rock strikes the ground, what is its kinetic energy?
twice that of the first rock
four times that of first rock
the same as that of the first rock
half that of the first rock

Dillan Perez

$K.E.=\frac{1}{2}m{v}^{2}$
Kinetic energy of first rock will be $\left(K.E\right)FR=\frac{1}{2}m{v}^{2}$ …(1)
Kinetic energy of second rock will be $\left(K.E\right)SR=\frac{1}{2}\left(2m\right){v}^{2}$ …(2)
$\frac{\left(K.E\right)}{FR}=\frac{\frac{1}{2}m{v}^{2}}{\frac{1}{2}\left(2m\right){v}^{2}}$
$⇒$$\frac{\left(K.E\right)}{FR}=\frac{1}{2}$
$⇒$ $\left(K.E\right)SR=2\left(K.E.\right)FR$
Answer is twice that of the first rock.

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