. 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?

 

Best Answer

Sol. We know that,

Kinetic energy = 1/2mv2

25 = 1/2× m × (5) 2

25 = 1/2× m × 25

m = 25 x 2 /25

 = 2 kg

In the first case, the velocity of 5 m/s is doubled

So the velocity becomes 5×2 = 10 m/s

Kinetic energy = 1/2 mv2

 = × 2 × (10) 2

 = × 2 × 100

 = 100 J

Therefore, when the velocity is doubled, then its kinetic energy becomes 100 J

In the second case, the velocity of 5 m/s is increased three times.

So the velocity becomes 5×3 = 15 m/s

Kinetic energy = mv2

 =1/2 × 2 × (15) 2

 =1/2 × 2 × 225

 = 225 J

Therefore, when the velocity of object is increases three times, then its kinetic energy becomes 225 J

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