What is Energy?

The ability to do work or cause change.

WORK: is the amount of energy needed to make something move by applying some force over some distance. Work = FORCE (N) X DISTANCE(m) = Joules 1 Joule = 1 Newton*meter

Amount of work done depends on: 1.The FORCE applied 2.The DISTANCE that force causes the object to move

The force and distance must be in the SAME direction If an object does not move, NO WORK HAS BEEN DONE

POWER: The rate at which energy is changed from one form to another; the rate at which work is done. Power = Work done (Joules) = watts Time Interval (seconds)

Therefore, a high-powered engine delivering two times the power of a regular engine does TWICE as much work in the same amount of time.

Practice Problem How much work is produced when a 1000 N force is applied over 4 meters? –W=F*d –W=1000 N * 4 m –W=4000 J

Forms of Energy Energy has a number of different forms, all of which measure the ability of an object to do work on or change another object. In other words, there are different ways that an object can possess energy.

Two States of Energy Kinetic energy Potential Energy

Kinetic Energy Kinetic energy is the energy of motion. Kinetic energy is measured by how much work is done to put an object in motion or to rest.

Kinetic Energy (KE): the energy of a MOVING OBJECT that is capable of doing work. KE = ½ mass (kg) X velocity2 (m/s)2 KE= ½ mv2

Depends on the mass and speed of the object. Therefore, HEAVIER OBJECTS will have more KE than LIGHTER objects traveling at the same speed. Also, a car moving 2X as fast will have FOUR TIMES the KE because THE SQUARE OF THE SPEED EFFECTS THE KE.

Work Energy Theorem: The change in KE of a system is equal to the amount of WORK done. Work = Change of KE W= KE

Kinetic energy

Potential Energy Potential energy is energy due to position or stored energy. Potential energy is also called gravitational potential energy.

Potential Energy (PE): Energy that is STORED; ready to do work  Gravitational Potential Energy: The stored energy in an elevated object EQUAL to the amount of WORK done to elevate it against GRAVITY.

PE = mass (kg) X gravity (m/s/s) X height (m)  PE= mgh

Potential energy

Gravitational Potential Energy

Can something have both potential and kinetic energy?

An example of something that has both potential and kinetic energy. A waterfall has both kinetic and potential energy. The water at the top of the waterfall has stored potential energy. Once the water leaves the top of the waterfall, the potential energy is changed into kinetic energy.

Law of Conservation of Energy Energy cannot be created or destroyed; it can only be changed from one of form of energy to another form. The amount of energy stays the same.

What are the different forms of Energy? Kinetic Energy Potential Energy Thermal, or heat energy Chemical Energy Electrical Energy Radiant Energy (light) Sound Energy Nuclear Energy Mechanical Energy

Changing from one form of energy to another

Energy Transformations Burning coal – chemical to ? Phosphorescence (firefly) – chemical to ? Playing a violin – mechanical to ? Turning on a lamp – electrical to ?

How do we use energy? Heat buildings To generate electricity Power cars and trucks

How many sources of energy can you name? Coal Petroleum (oil) and natural gas Nuclear Solar Wind Hydropower (from moving water) Biomass (from plants, including wood) Geothermal (from heat inside the earth)

Hydropower q_UMMhttp:// q_UMM

What is a fossil fuel??? Fuel that comes from the remains of prehistoric living organisms Plants and animals lived long before dinosaurs

What are examples of fossil fuels? Coal Petroleum (oil) Natural gas

Non-renewable sources Sources that are limited and can run out

Which sources are not renewable? Fossil fuels: coal, oil, natural gas Nuclear

Renewable Energy Energy sources that are replaced by natural processes at a rate equal to their use

Which sources are renewable? Solar Water (hydro-electric) Wind Biomass (plants)

How much of our energy consumption is from renewable sources? 6.4%