Question

A ball mass $0.20kg$ is thrown vertically upwards with an initial velocity of $20m{s}^{-1}$. Calculate the maximum potential energy it gains as it goes up.

• A. $80J$
• B. $40J$
• C. $0J$
• D. $-40J$

Answer 1

The correct option is B $40J$

$K.E=\frac{1}{2}\times m\times v^2$
$K.E=0.5\times 0.2\times 20\times 20=40J$
As it has $40J$ at initial point as total energy, at some point $X,P.E$ is maximum.
$Totalenergy=P.E+K.E$
$40=P.E+K.E$
As energy is conserved, total energy at point $X$ also must be $40J$. For $P.E$ to be maximum $K.E$ must be zero.
Hence $P.E=40J$
We can come to the conclusion that it will have the maximum value at maximum height.