## Work, Energy and Power

CHAPTER REVISION TEST

CLASS XI - PHYSICS

**Q1**: When an air bubble rises in water, what happens to its potential energy? [1]

**Q2**: A spring is cut into two equal halves. How is the spring constant of each half affected? [1]

**Q3**: What should be the angle between the force and the displacement for maximum and minimum work? [1]

**Q4**: The momentum of an object is doubled. How does it’s. K.E. change? [1]

**Q5**: What is work done in holding a 15kg suitcase while waiting for a bus for 15 minutes? [1]

**Q6**: In which motion momentum changes but K.E. does not? [1]

**Q7**: A light body and a heavy body have same kinetic energy. Which one has greater linear momentum? [2]

**Q8**: A light body and a heavy body have same linear momentum. Which one has greater K.E.? [2]

**Q9**: Can a body have energy without momentum? [2]

**Q10**: Obtain an expression for K.E. of a body moving uniformly? [2]

**Q11**: A particle moves along the x – axis form x = 0 t x = 5m influence of force given by F = 7 – 2x + 3x².

Calculate the work done in doing so. [2]

**Q12**: A body of mass 3kg makes an elastic collision with another body at rest and continues to move in the original direction with a speed equal to one – third of its original speed. Fine the mass of the second body. [2]

**Q13**: What is meant by a positive work, negative work and zero work? Illustrate your answer with example? [3]

**Q14**: Show that for a freely falling body the sum of its kinetic energy and potential energy remains constant at all points during its fall? [3]

**Q15**: A body of mass 2kg initially at rest moves under the action of an applied force of 7N on a table with coefficient of kinetic friction = 0.1. Calculate the

ⅰ Work done by the applied force in 10s

ⅱ Work done by the friction in 10s

ⅲ Work done by the net force on the body in 10s. [3]

**Q16**: Ball A of mass m moving with velocity U collides head on with ball B of mass m at rest. If e be the coefficient of restitution then determine the ratio of final velocities of A and B after the collision. [3]

**Q17**: If the momentum of the body increases by 20% what will be the increase in the K.E. of the body? [3]

**Q18**: Derive the expression for the potential energy stored in a spring? [3]

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