Mass of the object = m, velocity of the object = 5ms^-1, kinetic energy E_k = 25J

and E_K = 1/2 mv²

So, 25 = 1/2 (5)²m

m = (25 x 2)/25

m = 2 kg

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Case (i) when the velocity is doubled.

Mass of the object = m = 2 kg

And, v = 2 × 5ms^-1 = 10ms^-1

∴ Kinetic energy (E_K) = 1/2 mv²

(E_K) = 1/2 x 2 x 10²

E_K = 100J

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Case (ii) when the velocity is increased three times

i.e., v = 3×5

v = 15ms^-1

m = 2 kg

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Kinetic energy (E_K) = 1/2 mv²‍

(E_K) = 1/2 x 2 x 15²

(E_K) = 225J