NCERT CLASS IX - Science Textbook
Chapter 11 - Work and Energy
The kinetic energy of an object of mass, mmoving with a velocity of 5 m s - '1is 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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velocity = v = 5 m/s
mass = m
Kinetic energy = 1/2 m v²
1/2 m * 5² = 25 Joules
=> m = 2 kg
When the velocity v is doubled, since there is v² in the expression for KE., KE becomes 2² = 4 times.
So the KE will be 25 J * 4 = 100 Joules.
when the velocity is increased to 3 times its original value: ie., 15 m/sec, its KE is 3² = 9 times , hence, 9 * 25 J = 225 Joules.
mass = m
Kinetic energy = 1/2 m v²
1/2 m * 5² = 25 Joules
=> m = 2 kg
When the velocity v is doubled, since there is v² in the expression for KE., KE becomes 2² = 4 times.
So the KE will be 25 J * 4 = 100 Joules.
when the velocity is increased to 3 times its original value: ie., 15 m/sec, its KE is 3² = 9 times , hence, 9 * 25 J = 225 Joules.
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