Question

3. The kinetic energy of an object of
mass, m moving with a velocity
of 5 ms' 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?

Answer 1

Answer:

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Explanation:

Here, kinetic energy of the object, Ek=25J

velocity of the object, υ=5m/s

AsEk=12mυ2,m=2Ekυ2=2×25J(5/s)2=2kg

Kinetic energy of the object when its velocity is doubled (i.e.,υ=10m/s)

12mυ2=12(2kg)(10m/s)2=100J

Kinetic energy of the object when its velocity in increased three times (i.e.,υ=15m/s)

=12mυ2=12(2kg)(15m/s)2=225J

Aliter. Since Ek∝υ2 (as m is constant), (i) when υ is doubled, Ek becomes (2)2=4 times its previous value, i.e.,4×25J=100J (ii) when υ is increased three times, Ek becomes (3)9=9 times it previous value, i.e., 9×25J=225J