Question

Kinetic energy of a body moving with speed 10 m/s is 30 J. If its speed becomes 30 m/s, its kinetic energy will be 

(1) 10 J 

(2) 90 J 

(3) 180 J 

(4) 270 J

Answer 1

Correct option is (4) 270 J

\(KE \propto v ^2\)

⇒ \(KE' = KE \times \frac {v^2}{v}\)

\(= 30 \times \frac {30 ^2}{10}\)

\(= 270 \,J\).