CBSE Class 9 Science Notes Chapter 11 Work,
Power and Energy
Facts that Matter
Work: When a force acts on an object and the object shows displacement, the force has done work
on the object.Two conditions need to be satisfied for work to be done:(i) A force should act on
object(a) The object must be displacedWork = Force x Displacement Unit of work done = Joule =
Newton x metre 1 Joule work is said to be done when 1 Newton force is applied on an object and it
shows the displacement by 1 meter.
EnergyThe capacity of a body to do work is called the energy of the body.Unit of energy = Joules
1KJ = 1000 J
Forms of Energy: The various forms of energy are potential energy, kinetic energy, heat energy,
chemical energy, electrical energy and light energy.
Kinetic Energy: Energy possessed by a body due to its motion. Kinetic energy of an object
increases with its speed.Kinetic energy of body moving with a certain velocity = work done on it to
make it acquire that velocity
DerivationLet an object of mass m, move with uniform velocity u, let us displace it by s, due to
constant force F, acting on it
, Potential EnergyThe energy possessed by a body due to its position or shape is called its potential
energy.shape
Power and Energy
Facts that Matter
Work: When a force acts on an object and the object shows displacement, the force has done work
on the object.Two conditions need to be satisfied for work to be done:(i) A force should act on
object(a) The object must be displacedWork = Force x Displacement Unit of work done = Joule =
Newton x metre 1 Joule work is said to be done when 1 Newton force is applied on an object and it
shows the displacement by 1 meter.
EnergyThe capacity of a body to do work is called the energy of the body.Unit of energy = Joules
1KJ = 1000 J
Forms of Energy: The various forms of energy are potential energy, kinetic energy, heat energy,
chemical energy, electrical energy and light energy.
Kinetic Energy: Energy possessed by a body due to its motion. Kinetic energy of an object
increases with its speed.Kinetic energy of body moving with a certain velocity = work done on it to
make it acquire that velocity
DerivationLet an object of mass m, move with uniform velocity u, let us displace it by s, due to
constant force F, acting on it
, Potential EnergyThe energy possessed by a body due to its position or shape is called its potential
energy.shape
