CBSE  /  Class 9  /  Science  /  Work and Energy

  • 1. 
    Two army persons A and B each of weight of 500 N climb up a rope through a height of 10 m. A takes 20 s while B takes 40 s to achieve this task. What is ratio of the powers of person A and B?

  • 1 : 2
  • 1 : 4
  • 2 : 1
  • 14 : 1

  • 2. 
    If speed of a car becomes 2 times, its kinetic energy becomes

  • 4 times
  • 8 times
  • 16 times
  • 12 times

  • 3. 
    Work done by friction

  • increases kinetic energy of body
  • decreases kinetic energy of body
  • increases potential energy of body
  • decreases potential energy of body.

  • 4. 
    When a coil spring is compressed, the work is done on the spring. The elastic potential energy

  • increases
  • decreases
  • disappears
  • remains unchanged

  • 5. 
    One joule work is said to be done when

  • a force of 1 N displaces a body by 1 cm
  • a force of 1 N displaces a body by 1 m
  • a force of 1 dyne displaces a body by 1 m
  • a force of 1 dyne displaces a body by 1 cm.

  • 6. 
    SI unit of power is

  • watt
  • joule
  • newton
  • metre

  • 7. 
    Mechanical energy of a body includes

  • kinetic energy only
  • potential energy only
  • kinetic energy and potential energy
  • none of these

  • 8. 
    Commercial unit of energy is

  • joule
  • kWh
  • watt
  • newton

  • 9. 
    Potential energy of a body depends on its

  • position
  • configuration
  • position and configuration
  • mass and velocity
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