Question

On increasing the speed of a body to 2 ms its kinetic energy is quadrupled.Then its original speed must be

Answer 1

Let  K = 1/2 M V ^2

On increasing speed to 2 ms−1.

K′=1/2 M× 2^2 = 4*K

⇒1/2 M 4=4×1/2 M V ^2

⇒V=1 m/s

Answer 2

Let  K = 1/2 M V ^2

On increasing speed to 2 ms−1.

K′=1/2 M× 2^2 = 4*K

⇒1/2 M 4=4×1/2 M V ^2

⇒V=1 m/s