Question

If the mass of the moving object is decreased 1/4 of its mass and its velocity is increased to twice its previous velocity, what will be the kinetic energy of the object from the following?

• A. 1/2 of the previous kinetic energy
• B. 4 times of previous kinetic energy
• C. Kinetic energy will remain constant
• D. 2 times of the previous kinetic energy

Answer 1

Answer: (C)

Kinetic energy will remain constant

K.E = $\frac{1}{2}m{v}^2$

New K.E = $\frac{1}{2}$ ($\frac{1}{4}m$) $(2v{)}^2$ = $\frac{1}{2}$ ($\frac{1}{4}m$) $4v^2$ = $\frac{1}{2}$$m{v}^2$.

Hence, kinetic energy will remain constant.