Question

. A 4kg mass which is under motion in a straight line slowed down such that its kinetic energy has been decreased from 72J to 8 J. Then the decrease in velocity is -----m/s​

Answer 1

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Class 11

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>>Work, Energy and Power

>>Work Energy Theorem

>>The velocity of a car increases from 54

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The velocity of a car increases from 54km/h to 72km/h. If the mass of the car is 1500kg, find the work done to increase the velocity.

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Correct option is B)

Initial Velocity, u=54km/hr=15m/s

Final velocity , v=72km/hr=20m/s

Mass =1500kg

Initial kinetic energy

2

1

mu

2

⇒

2

1

1500×15×15=168750J

Final kinetic energy

2

1

mv

2

⇒

2

1

1500×20×20=300000J

So, change in kinetic energy = work done=300000−168750=131250J