Question

The kinetic energy of an object of mass m, moving with a velocity of $5m{s}^{-1}$ is 25 J. What will be its kinetic energy when its velocity is tripled?

• A. $125J$
• B. $225J$
• C. $100J$
• D. $500J$

Answer 1

Answer: (B)

$225J$

Given, $velocityofobject,v=5m{s}^{-1}$;
$kineticenergyofanobject,E_K=25J$
$E_K=\frac{1}{2}m{v}^2$ or $25=\frac{1}{2}\times m\times (5{)}^2$
or $m=\frac{50}{25}=2kg$
When the velocity triples,
$E_K=\frac{1}{2}m{v}^2=\frac{1}{2}\times 2\times (15{)}^2=225J$