Work, Energy, and Power - Class 9 Lecture Notes

These flashcards cover key concepts from the lecture on Work, Energy, and Power for Class 9, focusing on definitions, formulas, and principles discussed.

What is the formula for Work done when a force acts on an object?

W = F.s, where W is work, F is force, and s is displacement.

What is the unit of Work?

The unit of work is Newton metre (Nm) or Joule (J).

When is the work done considered positive?

When both the force and displacement are in the same direction.

What causes the work done to be zero?

If a force acting on a body causes no displacement.

Define Energy.

The capacity of a body to do work.

List the forms of energy mentioned in the notes.

Potential energy, Kinetic energy, Heat energy, Electrical energy, Light energy, Chemical energy.

What is Kinetic Energy?

The energy possessed by a body due to its motion.

What is Potential Energy?

The energy possessed by a body due to its position or shape.

What does Gravitational Potential Energy (GPE) refer to?

The energy possessed by an object when work is done in raising it against gravity.

What is the Work-Energy Theorem?

The net work done by the forces on an object equals the change in its kinetic energy.

State the Law of Conservation of Energy.

Energy can neither be created nor destroyed; it can only be converted from one form to another.

What is Power?

The rate of doing work.

How is commercial energy measured?

In kilowatt-hours (kWh), where 1 kWh = 1 kilowatt x 1 hour = 3600000 Joules.