Energy and Its Forms Energy = ability to do work Work = when a force moves an object through a distance, transfer of energy

Kinetic Energy = energy of a moving object KE = 1/2 mv 2 m = mass (kg) V = velocity (m/s)

Potential Energy = stored energy Gravitational potential energy = potential energy due to mass, height, and gravity PE = mgh m = mass (kg) h = height (m) g = acceleration due to gravity = 9.8 m/s2

Elastic potential energy = energy due to stretch or compression Spring Bouncing ball Bow & Arrow

4. Forms of Energy

A. Mechanical = energy associated with motion and position of everyday objects ME = PE + KE B. Thermal = total potential and kinetic energy of particles in an object - Energy in movement of molecules or atoms

C. Chemical = energy stored in chemical bonds D. Electrical = energy associated with electric charges E. Electromagnetic = photon energy which travels in waves (as light) F. Nuclear = energy stored in the nucleus of the atom due to forces between protons and neutrons

Energy Conservation Law of conservation of Energy = energy can be converted into different forms, but never destroyed Calculations Total mechanical energy ME = PE + KE KE before + PE before = KE after + PE after ME (before) = ME (after)

PE KE PE+KE KE

PE at top = KE at bottom KE + PE (before) = KE + PE (after) Ex 1: Falling Objects Falling from rest, no air resistance PE g = mgh g = 9.8 m/s 2 h = 20 m = 80 kg mgh = 1/2 mv 2 (80kg)(9.8m/s 2 )(20m) = 1/2 (80kg)v J = 1/2 (80kg)v m 2 /s 2 = v m/s = v

Energy Conversion = change from one form to another. Process of doing work. Chem->Kinetic->elastic potential->Kinetic Chemical->Electrical->Electromagnetic Electromagnetic->Electrical->Electromagnetic Electrical->Electromagnetic->Thermal Chem->Kinetic->Electromagnetic, Thermal Potential->Kinetic->Potential->Kinetic->Potential Electromagnetic->Chemical Chemical->Thermal->Kinetic->Electrical

Chemical ThermalKinetic Electrical

Some energy is not always converted when work is being done. Energy can be lost to the environment as heat. Examples: - A car burning gasoline - An electric light giving off heat

Energy Resources Nonrenewable Energy Resources = exist in limited quantities, cannot be replaced in a human lifetime. Fossil fuels – Forms from the remains of plant material, buried millions of years ago. Includes coal, natural gas, and petroleum (oil). Fossil Fuel Formation

Nuclear Energy Uranium fuel – Converts nuclear energy to heat

Hydroelectric Energy = energy from flowing water

Solar Energy Passive = without machinery Active = with machinery

Geothermal Energy = thermal energy beneath Earth’s surface.

Biomass Energy = chemical energy stored in living things Ex: Wood, peat, corn stalks Hydrogen Fuel Cell = device that reacts hydrogen with oxygen to produce electricity

Wind turbine Converts kinetic energy of wind into electrical energy.