Machines and living things convert stored energy to motion and heat. Energy from
the Sun can be changed into other forms of energy. Electricity comes from
several sources, but all of them can be traced back to energy from the Sun.
Electricity is carried through wires to places where it is used, like our homes.
Here it is changed into heat, light, motion and other forms.
Machines use energy to produce motion and heat. Fuel is the
energy source, which a car, plane, train or a boat uses to produce motion. Have
you touched the hood of a car after a long trip? As the engine converts the fuel
into motion, heat is also produced.
Humans and animals convert food energy into the energy of
motion and heat, when you eat a turkey sandwich, the energy contained in it
gives you the energy, you need to walk, play football or run across the
schoolyard. The body also uses the food to produce thermal energy to keep you
warm, when you play outside on a cold day, you gradually feel warm because the
energy of motion produces heat. So it is better to move around on cold days than
to stand still.
  
Energy is the ability to do work and to cause something to move and change.
Energy can be found in several forms, chemical and mechanical. Living things and machines cannot work without energy. Forms of
energy can be transferred from one form to another, but Energy cannot be created
or destroyed. The use of Energy and the loss of Energy usually end up as Heat.
Motion: Motion is a change in the position or location of an object with respect to
time.
Heat: Heat is a form of energy that is generated by a difference in temperature.
Energy and motion: Energy is needed to cause changes. This can involve changing the shape of
matter, or changing the speed or direction of an object’s motion.
Examples associated with energy of motion, such as walking and
running, water wheels, wind-up toys, windmills, toy cars and trucks, rolling or
thrown balls, motors, vibrating devices (like a doorbell or buzzer), vibrating
strings on a guitar or other musical instruments.
 
There are two types of energy:
1. Potential Energy- It is the energy possessed by the body by virtue of
its position.
2. Kinetic Energy- It is the energy possessed by the body by virtue of
its motion.
Potential Energy is stored energy, or energy of position. Anything may have
stored energy that gives it the potential to cause change, if certain conditions
are met. The amount of Potential Energy that a sample of matter has depends on its
position or condition. Springs in toys are the example of potential
energy.
Potential Energy is changed to Kinetic Energy upon movement. Kinetic Energy is
energy in the form of motion.
Simple Machines: Simple
machines help us make better use of our muscle power to do work. A machine
produces force and controls the direction of force. It cannot create energy.
Simple Machines help us lift, pull, increase elevation of heavy things, change
the direction of the force, increase the force, split things, fasten things, and
cut things.
 
We all use simple machines everyday for opening a door,
turning on the water faucet, going up the stairs, or opening a can of paint.
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