Question

calculate the decrease in the kinetic energy of a moving body if its velocity reduces to one by third of the initial velocity

Answer 1

kinetic energy is half mass *velocity squared

ke=1/2*m*v*v
the velocity now changes to v/3
new ke=1/2*m*v/3*v/3
ratio of ke to new ke=mv2/2:mv2/18=9:1
so the new ke is 1/9 times that Of the previous value

Answer 2

solution.

kinetic energy= 1/2 m v^2

when body moves with v velocity.

the kinetic energy= 1/m v^2

when body moves with 1/3 v velocity.

then kinetic energy= 1/2 m (1/3v)^2

= 1/2 m 1/9v^2

now, kinetic energy decreased=( 1/2 mv^2) - (1/2 m 1/9 v^2)

=> v^2 - 1/9 v ^2

= (9v^2 - 1 v^2)/9

= 8/9 v^2 joule


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