Work & Energy Flashcards
(38 cards)
what is work? unit? formula?
when a force acting on a body displaces it in the direction of force.
joule (J)
W=F x S
define joule?
one joule equals to the work done by 1N force that displaces a body through 1m distance.
unit of work and energy
J= N x m
what is energy? formula for K.E.
a body possesses energy if it has the ability to do work.
what is kinetic energy? derive its formula.
the energy possessed by a body due to its motion.
FTB book
formula shows K.E possessed by a body of mass m moving with velocity v.
what is P.E? derive its formula? unit?
the energy possessed by a body due to its position or change in configuration.
Joule
what is gravitational potential energy?
the energy possessed by an object due to a change in its position when it is present in a gravitational field.
by doing work against force of gravity, an object has been given a special form of P.E called gravitational P.E
name & describe all forms of energy?
7
what is chemical energy? examples?
energy stored in a substance that is released through a chemical reaction.
fuels and food.
they have chemical energy & when they burn (chemical reaction), they release energy in the form of heat & light
food is fuel (chemical energy), inside the body it releases energy in the form of ATP and release heat
what is mechanical & heat energy? examples?
the energy possessed by a body both due to its motion or position. examples: water fall, wind, a moving car, a lifted hammer, a stretched bow, a catapult, compressed spring.
heat energy is given out by hot bodies.
burning fuel. frictional force, food intake, sun
define light & sound energy? examples?
a kind of kinetic energy with the ability to make types of light visible to human eyes. plants produce food in the presence of light. candles, bulb, burning fuel, sun.
S.E is produced by vibrations.
examples: vibrating diaphragm of drum, vibrating strings of sitar & vibrating air column of wind instruments such as flute.
define E.E and N.E? examples?
widely used form of energy.
supplied by wires. examples: batteries & electric generators. electric generators are run by hydro, thermal or nuclear power.
N.E is released in the form of nuclear radiations. H.E released during nuclear reactors is converted to electrical energy. The energy coming from the Sun is the result of nuclear reactions taking place in the Sun.
H.E released by nuclear reactions converted into E.E
example of interconversion of energy?
page 127
heat energy from sun taken by oceans. thermal energy causes water to evaporate to form water vapors. These vapors forms clouds.
state the law of conservation of energy?
the amount of energy is neither created nor destroyed, it can only be transformed from one form to another, but the total amount of energy remains constant.
2 examples of interconversion of energy?
generation of electricity:
a cyclist going up to the top of a hill.
what is dissipated energy?
Any energy that is not transferred to useful energy stores is said to be wasted because it is lost to the surroundings.
aka lost energy= not used in anything
all of the energy we get comes directly or indirectly from ______________.
can work done be -ve?
the Sun
yes, if the object is moving in the opposite direction to the direction of the applied force. cos 180 = -1. so the angle should be 180 for the work to be -ve
what are fossil fuels?
Fossil fuels are made from decomposing plants and animals. These fuels are found in Earth’s crust and are usually hydrocarbons which can be burned for energy. Coal, oil, and natural gas are examples of fossil fuels
what is oil? why is oil preferred source of energy over coal?
oil/crude oil refines into many different energy products such as gasoline/petrol, jet fuel, heating oil
because oil produces more energy than same amount of coal.
oil=crude oil
gasoline=petrol
petroleum= curde version of petrol
methane is a __________.
natural gas which is byproduct of oil.
advantage of natural gas: easy to transport
typically natural gases are mixture of gases.
byproduct: a secondary product made in the manufacture of something.
what happens when fossil fuels are burnt?
C+O=
hydrocarbon+ O=
they combine with O from the air. The carbon become CO2 hydrogen becomes water. while energy is released as heat.
CO2 + heat energy
CO2 + H2O+ heat energy
where does energy come from in nuclear power plants?
In nuclear power plants, we get energy as a result
of fission reaction.
During fission reaction, heavy atoms, such as Uranium atoms, split up into smaller parts releasing a large amount of energy.
Nuclear power plants give out a lot of nuclear radiations and vast amount of heat.
A part of this heat is used to run power plants while lot of heat goes waste into the environment.
name renewable energy sources.
Solar energy from the sun.
Hydropower from flowing water.
sunlight & water
how can energy be obtained from water?
Dams serve meany purposes. They help to control floods by storing water. The water stored in dams can be used for irrigations & also create electrical energy.
how can energy be obtained from the sun?
the energy from direct sunlight can be used to produce electricity. Solar cells are used to power everything. But just like wind energy, significant land area is required to produce large amounts of electricity.
