1. Energy can be converted from one form to another but cannot be created or destroyed. Common conversions include electrical to thermal energy in heaters and mechanical to electrical in turbines. 2. Energy is measured in joules and defined as the ability to do work or cause change. The total amount of energy in the universe remains constant as it changes forms. 3. Work is done when a force causes an object to move through a distance, and is measured in newtons or joules. Work transfers energy to an object and depends on both the applied force and displacement.

1. Energy, Work and Power
Energy: Energy can neither be generated nor it can be destroyed. It can only be converted from
one form to another. For example, in a room heater, electrical energy is converted to the thermal
energy. Turbine converts mechanical energy stored in steam to electrical energy.
Nature of Energy: Because of the direct connection between energy and work, energy is
measured in the same unit as work: joules (J). In addition to using energy to do work, objects
gain energy because work is being done on them.
Conservation of Energy: Energy can never increase or decrease. Energy can change from
one form to another. But the total amount of energy in the universe remains the same. Energy
is that it is constantly being changed and recycled from one form to another
WORK: Work is done whenever a force (F) is exerted and whenever there is displacement (s).
(s). The amount of work done is proportional to both the force and displacement. (W = F x s)
Work is measured in newton-meters. Newton- 1 joule of work = 1 newton of force x 1 meter
of distance James Prescott Joule
WORK - Is the amount of force applied to an object over a distance
WORK IS NOT DONE WHEN :- The object is stationary - No force applied on the object in the
direction of the motion - The direction of the motion of the object is perpendicular to that of
the applied force - When work is done and energy is transferred to the object
 Work is the transfer of energy that occurs when a force makes an object move.
 2 conditions for work to be done An applied force must make the object move 
Movement must be in the same direction as the force.
ENERGY AS WORK: Energy is work or the capacity to perform work .Work is when a force is
applied to an object so that it moves a distance.
W = Fx
Where, W – work in Joules (J), F – force in Newton (N), x – distance moved in meters (m)
ELECTROMAGNETISM:every atom is held together by positive and negative electrical charges
.a form of electromagnetic energy .The energy from our sun is transmitted to the Earth via
electromagnetic waves. Electromagnetic energy only exists as radiant energy from the sun and
stars.
NUCLEAR ENERGY: strong nuclear force holds the protons and neutrons together at the core
of the sun, atoms fuse and in the process release energy process is called fusion. the energy
from a nuclear bomb, and from nuclear reactors released by the splitting apart of the nucleus
of atoms .This is called fission.

2. CHEMICAL ENERGY: The source of all energy for all living things is in a chemical process
called photosynthesis. electromagnetic waves provide the energy to convert water, and carbon
dioxide from the air, into oxygen and glucose .Glucose is used as energy by the plant and
animals that the eat the plant Advantage of chemical energy is it can be stored as potential
energy for long periods of time and then released as kinetic energy
SOUND ENERGY: sound is a form of kinetic energy .sound energy radiates outwards,
transmitted from molecule to molecule
THE ENERGY OF HEAT: Heat is a form of kinetic energy .rapid movement of molecules as the
heat of an object increases, the molecules move more and more rapidly.
ENERGY EXCHANGES: Heat is a by-product of the mechanical or chemical processes
THE LAWS OF THERMODYNAMICS:
First Law: energy cannot be created or destroyed
Second Law: All things are moving towards equilibrium
Third Law: As a system approaches absolute zero, the extraction of energy becomes more and
more difficult.
THE ENERGY-MATTER CONNECTION:matter can be transformed into pure energy .Energy
can be created and sometimes destroyed.
Kinetic energy is described as energy of matter in motion. Two factors governing an object’s
kinetic energy: energy: – Kinetic energy is proportional to the mass – Kinetic energy increases
as the square of its velocity Kinetic energy equals the mass of the moving object times the
square of that object’s velocity, multiplied by the constant ½. Kinetic energy (joules) = ½ X
mass (kg) x [Velocity (in m/s)]2 KE = ½ mv2
Potential energy Potential energy is the energy that could result in the exertion of a force
over a distance. Energy on account of their position Stored energy Most common =
gravitational PE.
Potential Energy is stored energy. Stored chemically in fuel, the nucleus of atom, and in foods.
Or stored because of the work done on it: Stretching a rubber band. , Winding a watch. , Pulling
back on a bow’s arrow, lifting a brick high in the air. Potential energy is not important in the
total amount of energy available in the universe.
Einstein's formula of E = mc² states that energy equals mass times the speed of light squared
Kinetic Energy depends on speed and Mass.
Kinetic energy= mv²/2
where, M=mass of object, V= objects speed
The faster something is moving, the more kinetic energy it has. The more massive a moving

3. object is, the more kinetic energy it has. Speed has a greater effect on kinetic energy than
mass does.
Gravitational Potential Energy depends on weight and height.
Gravitational Potential Energy=weight x height
Mechanical Energy: Energy due to an object’s motion (kinetic) or position (potential).
Mechanical Energy- is the total energy of motion and position of an object. Mechanical energy
can be all potential energy, all kinetic energy or some of both. Mechanical Energy= potential
energy + kinetic energy
Mechanical energy is due to the position and motion of the object. The mechanical energy does
not change because the loss in potential energy is simply transferred into kinetic energy.
Friction causes some of the mechanical energy of the swing to change to thermal energy and
the temperature of the hooks and chain heat up a little.
Light energy: Includes energy from gamma rays, x-rays, ultraviolet rays, visible light, infrared
rays, microwave and radio bands
Electrical Energy: Energy caused by the movement of electrons .Easily transported through
power lines and converted into other forms of energy
Heat energy: The heat energy of an object determines how active its atoms are. A hot object is
one whose atoms and molecules are excited and show rapid movement. A cooler object's
molecules and atoms will show less movement.
Energy Transformations and Conservation: A change from one form of energy to another is
called an energy transformation. Some energy changes involve single transformations, while
others involve many transformations. Most forms of energy can be transformed into other
forms
Single Transformations: Sometimes, one form of energy needs to be transformed into another
to get work done.
Your body transforms the chemical energy in your food to mechanical energy you need to
move your muscles. Chemical energy in food is also transformed to the thermal energy your
body uses to maintain its temperature.
Multiple Transformations: Often, a series of energy transformations is needed to do work. For
example, the mechanical energy used to strike a match is transformed first to thermal energy.
The thermal energy causes the particles in the match to release stored chemical energy, which
is transformed to thermal energy and the electromagnetic energy you see as light.
Types of energy: Energy can be broadly classified into two types:-• Renewable Resources
• Non-renewable Resources
Types of Renewable Energy: Solar energy, Wind energy, geothermal energy, Hydro energy

4. NONRENEWABLEENERGY:Non Renewable energy cannot be generated again and again e.g.
energy generated from combustion of fossil fuels, energy from coal and gas etc.
Calories: A Calorie (C) is a unit to measure energy in foods. 1 Calorie is equal to about 4,184
Joules. A person uses about: 55 Calories while sleeping for 1 hour ,210 Calories while walking
for 1 hour ,850 Calories while running for 1 h.
Solar Energy :Solar energy can be converted into electrical energy by using solar panels, or
alternatively, be used as thermal energy using solar water heaters, solar cookers etc.
The Sun supplies 98% of the Earth’s energy.  The Sun is 75% hydrogen.  It releases energy
by a process called Nuclear fusion.  In Nuclear fusion, two hydrogen atoms come together to
form Helium. In the process, energy is released. This energy is the one that reaches the Earth
in form of light and heat (Electromagnetic energy).  It takes 8minutes for energy from the Sun
to reach the Earth.
Wind Energy: India is world’s third largest producer of electricity generation using wind
power by wind mills.
Hydro Energy: Using dams, water is allowed to pass through turbine blades, which produces
electricity. In India, after coal, most of the energy is produced by this method. .
Limited Fuels: At present consumption levels- Crude oil will last only for 40 years. Gas will
last for 60 years. Coal will be finished in nearly 200 years.
ENERGY CONSERVATION - is the act of using energy in a more efficient and effective
manner. - reducing energy through using less of an energy service. Renewable energy comes
from resources which are continually replenished such as sunlight, wind, rain, tides, waves and
geothermal heat. Non-renewable energy (also known as a finite resource) comes from resources
that does not renew itself at a sufficient rate for sustainable economic extraction in meaningful
human timeframes.
Gravitational Potential Energy The gravitational potential energy PE is the energy that an
object of mass (m) has by virtue of its position relative to the surface of the earth. The
gravitational potential energy of an object equals its weight (the force of gravity exerted on the
object) times its height above the ground (the object has been lifted above the surface of the
earth). Potential Energy (joules) = mass (kg) x g (m/s2) x height (m) PE = mgh
Work and Conservative Force: force is conservative when the work it does on a moving
object is independent of the path between the object’s initial and final positions. Force is
conservative when it does no work on an object moving around a closed path, starting and
finishing at the same point. The track exerts a normal force but the force is directed
perpendicular to the motion, hence, no work is done
Work and Non - Conservative Force A force is non conservative if the work it does on an object
depends on the path of the motion between the points. When an object slides over a surface,
the kinetic frictional force points opposite to the sliding motion and does

5. The rate of conversion of food energy to some other form is called metabolic rate. The total
energy conversion rate of a person at rest is called basal metabolic rate BMR of an individual
is related to thyroid activity The BMR is directly related to the mass of the person. Energy
consumption is directly proportional to oxygen consumption
Energy that is stored due to being stretched or compressed is called elastic potential energy.
Heat energy causes changes in temperature and phase of any form of matter.
Chemical energy is required to bond atoms together.
Fuel and food are forms of stored chemical energy.