This chapter explains the scientific meaning of work, energy, and power, and how they are closely connected. It clarifies that in science, work is done only when a force causes displacement in its direction. The chapter introduces energy as the capacity to do work and discusses its different forms such as kinetic energy and potential energy. It also explains how energy can change from one form to another while the total energy remains conserved. The concept of power is introduced to compare how fast work is done or energy is transferred. Through everyday examples, the chapter helps students understand how these ideas apply in real life.
Key Points
In science, work is done only when a force produces displacement.
Work is defined as the product of force and displacement in the direction of force.
Work done can be positive, negative, or zero.
The SI unit of work is joule (J).
Energy is the capacity of an object to do work.
The SI unit of energy is also joule (J).
Objects in motion possess kinetic energy.
Kinetic energy depends on mass and square of velocity.
Energy stored due to position or shape is called potential energy.
Gravitational potential energy depends on mass, height, and gravity.
Energy can change from one form to another.
According to the law of conservation of energy, energy is neither created nor destroyed.
The sum of kinetic and potential energy is called mechanical energy.
Power is the rate at which work is done or energy is transferred.
The SI unit of power is watt (W).
Greater power means work is done faster.
👉 👉Understanding work, energy, and power helps us recognise how nature and machines function efficiently. By learning how energy is used and conserved, we can use resources wisely, avoid wastage, and adopt responsible practices for sustainable living.