9th Science NCERT Chapter 10

Topics to Study from the Chapter on "Work and Energy":

1. Work

– Definition of work differs in daily use and in science

– Scientifically, work is done when there is a displacement of an object despite effort【4:0†source】.

2. Energy

– Different forms of energy: kinetic, potential, heat, chemical, etc.

– Mechanical energy is the sum of kinetic and potential energies【4:1†source】.

3. Power

– Rate of doing work

– SI unit is watt (W), where 1 W = 1 J/s【4:1†source】.

4. Law of Conservation of Energy

– Energy can be transformed from one form to another but not created or destroyed

– Total energy remains constant before and after transformations【4:3†source】.

5. Kinetic Energy

– Expression for kinetic energy of an object: \( E_k = \frac{1}{2}mv^2 \)

– Kinetic energy increases with the square of velocity【4:4†source】.

6. Energy Conversions

– Various instances of energy conversion in nature

– Activities and gadgets involving energy conversion【4:3†source】.

Students can use these summaries for revision.