Kinetic and Potential Energy

Kinetic Energy

• Kinetic energy is the energy of movement or motion

• To calculate kinetic energy you need to know an object’s mass and velocity

• Kinetic energy (KE) = ½ (m)*(v2) = ½ mv2

• Energy is expressed in Joules (J) which are kg*m2/s2

Example how to calculate kinetic energy

A 0.10 kg bird is flying at a constant speed of 8.0m/s. What is the bird’s kinetic energy?

Mass (m) = .10kgSpeed (v) = 8.0m/s2

KE = ½ (.10kg)* (8.0m/s)2

KE = 3.2 kg*m2/s2 = 3J

Kinetic Energy Equations

• If you are asked to solve for kinetic energy use• KE = ½ mv2

• If you are asked to solve for mass use• M = 2*(KE)/v2

• If you are asked to solve for velocity use• V = square root 2KE/m

Potential Energy

• Potential energy is the energy stored as a result of position

• Gravitational potential energy depends on an object’s height

Formula for calculating potential energy

• The formula is PEg = mgh = Fgh

• Fg will be in Newtons

• Where m = mass, g = gravity and h = height• In the second form • F = force in newtons(N), h = height• Gravitational potential energy is expressed in

Joules (J)

Example of calculating gravitational potential energy

• A diver at the top of a 10.0 m high diving platform has a mass of 50.0kg. What is her potential energy?

• PE = mgh• PE = (50.0kg)*(9.8m/s2)*(10.0m)• PE = 4900 kg*m2/s2 = 4900J

Potential Energy Equations

• If you are asked to solve for potential energy use• PE = mgh or PE = Fgh

• If you are asked to solve for mass use• m = PE/gh or m = PE/Fgh

• If you are asked to solve for height use• h = PE/mg or use h = PE/Fg

Elastic Potential Energy

• Elastic potential energy is the energy stored in an object that is stretched or compressed (think elastic)

• The energy is stored when the object is either stretched or compressed

Chemical Energy

• Chemical energy is the energy stored in chemical bonds

• The energy is released when the bonds are broken

Electric Energy

• Electric energy is the energy associated with electric charges

• Batteries contain electric energy

Nuclear Energy

• Nuclear energy is the energy stored in the nucleus of an atom

• Energy can be released by nuclear fission which is splitting the atom or by nuclear fusion which is joining nuclei