ICSE Class 10 Physics 2014 Solved Paper

Question : 8 of 66

Marks: +1, -0

Calculate the change in the Kinetic energy of a moving body if its velocity is reduced to

1 \/ 3

rd of the initial velocity.

Solution:

Given : Initial velocity

=v ;

Final velocity

=\;{v}/{3}

Initial kinetic energy

k_1=\;{1}/{2} × m × v^2

Final kinetic energy

k_2=\;{1}/{2} × m × (\;{v}/{3}) ^2

=\;{1}/{9} × \;{1}/{2} m v^2

Change in kinetic energy

\;=\;{1}/{2} m v^2-\;{1}/{9} × \;{1}/{2} m v^2

\;=\;{1}/{2} m v^2 (1-\;{1}/{9}) =\;{8}/{9} × (\;{1}/{2} m v^2)

=\;{8}/{9} × \;\text " Initial kinetic energy. "\;

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