Question

A body of mass (m) has a velocity (v). If the mass of the body increases 81 times, but the kinetic energy remains same, calculate the new velocity.

Answer 1

Kinetic energy remains constant, so

\[ \frac{1}{2}\, mv^{2} = \frac{1}{2}\, (81m)\, v_{1}^{2} \]

where v₁ is the new velocity.

\[ v^{2} = 81\, v_{1}^{2} \]

\[ v_{1} = \frac{v}{9} \]