## 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

Work done by the applied force in 10s
Work done by the friction in 10s
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]