NCERT Solutions for Class 9 Science Chapter 11: Work and Energy

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The NCERT Solutions for Class 9 Science Chapter 11 Work and Energy have been given in this article. Some of the important topics of Class 9 Science Chapter 11 Work And Energy include:

  1. Work Energy Theorem And Its Application
  2. Kinetic energy
  3. Thermal Energy

Download: NCERT Solutions for Class 9 Mathematics Chapter 11 pdf


NCERT Solutions for Class 9 Science Chapter 11


Important Topics for Class 9 Science Chapter 11 Work and Energy

Work is closely related to energy. The work–energy principle states that an increase in the kinetic energy of a rigid body is caused by an equal amount of positive work done on the body by the resultant force acting on that body. 

Work Energy Theorem and its Applications

Work can be defined as the transfer of energy into an object in order to cause it to move or displace. Energy can be expressed as the capacity to do work.

Example: State the Work-Energy theorem in brief.

Solution: The Work-Energy theorem expresses the following formula:
W = ΔKE = ½ mv2f − ½ mv2i

Here, 

  • vi = Particle speed before the application of force
  • vf = Particle speed after the application of force
  • m = Particle’s mass

Kinetic Energy

Kinetic Energy can be defined as the energy generated due to motion by an object. It can also be expressed as the energy that helps accelerate a body of rest to motion.

Example: What are the five major types of Kinetic Energy?

Solution: The five major types of Kinetic Energy are:

Thermal Energy

Thermal energy refers to the energy that a body is known to generate during when its atoms or molecules displace.

Example: What are two important points of Thermal Energy?

Solution: The two major points of Thermal Energy include:

  • The temperature of any given substance is found to hold a direct relationship with its thermal energy.
  • When the amount of heat present is in or out of the given object, then the thermal energy is seen to alter.

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CBSE X Related Questions

  • 1.
    How does the change in curvature of the eye lens help us in the process of seeing the nearby objects clearly?


      • 2.
        Briefly mention the steps in double-circulation through human heart.


          • 3.
            When an element 'X' reacts with water, it starts floating. Identify the element 'X':

              • Potassium
              • Calcium
              • Sodium
              • Iron

            • 4.
              Draw a neat diagram to show germination of pollen on the female reproductive part of the flower. Name and label only the following parts:
              (a) The part that receives the pollen grain.
              (b) The structure that carries the male germ cell to reach the female germ cell.


                • 5.

                  The reasons for excessive generation of wastes are:
                   (i) Use and throw policy. 
                  (ii) Increased availability of packaged food. 
                  (iii) Increased construction wastes. 
                  (iv) Non-sorting of dry and wet wastes

                    • (i), (iii) and (iv)
                    • (i), (ii) and (iii)
                    • (i), (ii), (iii) and (iv)
                    • (ii), (iii) and (iv)

                  • 6.
                    When a human egg is fertilized by a sperm having ‘Y’ chromosome, the zygote has the following combination of chromosomes:

                      • 44 + XX
                      • 22 + XX
                      • 44 + XY
                      • 22 + XY

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