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The kinetic energy of an object of mass, m moving with a velocity of 5 m s^-1 is 25 J. What will be its kinetic energy when its velocity is doubled?

The kinetic energy of an object of mass, m moving with a velocity of 5 \; m\; s ^{-1}  is 25\; J. What will be its kinetic energy when its velocity is doubled?

What will be its kinetic energy when its velocity is increased three times?

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Using the formula for the kinetic energy we have :

                                                          K.E\ =\ \frac{1}{2}mv^2

or                                                           25\ =\ \frac{1}{2}m\times 5^2

or                                                             m\ =\ 2\ Kg

(i) Kinetic energy when velocity is doubled :

                                                        K.E\ =\ \frac{1}{2}mv^2

                                                                    =\ \frac{1}{2}\times2 \times 10^2

                                                                    =\ 100\ J

(ii) Kinetic energy when velocity is tripled :

                                                         K.E\ =\ \frac{1}{2}mv^2

                                                                     =\ \frac{1}{2}\times 2\times 15^2

or                                                                 =\ 225\ J

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