Warm Up 9/19 What would require more power, running a mile or walking a mile? Which of these is are examples of doing work? Standing in place Running a marathon Sitting on the couch watching tv Walking your dog

Energy

Energy Energy is the ability to do work Without a source of energy, forces would be unable to move objects Energy can come from your muscles, from the food we eat, sound waves, etc.

Energy cont. There are two main categories energy can be classified as Kinetic Energy Potential Energy

Kinetic Energy Kinetic energy is the energy of motion When an object is in motion, we say that it has a kinetic energy

Kinetic Energy cont. The kinetic energy of any moving object depends on its mass and speed Kinetic Energy = 0.5 x m(v)2 m = mass v = velocity 0.5 = constant Kinetic Energy is measured in Joules

Kinetic Energy cont. Example: A bird that has a mass of 0.10 kg is flying at a constant speed of 8.0 m/s. What is the bird’s kinetic energy?

Kinetic Energy cont. Example Solved: First: isolate your mass and velocity variables Mass = 0.10 kg Velocity = 8.0 m/s

Kinetic Energy cont. Kinetic Energy = 0.5 x m(v)2 Kinetic Energy = 0.5 x 0.10kg(8.0 m/s)2 KE = 0.5 x 0.10kg (64 m/s2) KE = 0.5 x 6.4 kg(m/s2) KE = 3.2 kg(m/s2) KE = 3.2 J

Potential Energy Potential energy is the energy that is stored as a result of position It is stored energy with the potential to do work

Potential Energy Example There is potential energy stored within the string of the bow when it is pulled back It has the potential to do work if it is released

Potential Energy There are two types of potential energy Gravitational Potential Energy Elastic Potential Energy

Potential Energy Gravitational Potential Energy: Potential energy that depends on an object’s height Gravitational Potential Energy increases when an object is raised to a higher level

Potential Energy

Potential Energy Elastic potential energy: An object is said to be elastic if it springs back to its original shape after being stretched or compressed

Potential Energy Potential energy is created in an elastic object when it is stretched or compressed

Forms of Energy There are six major forms that energy can exist as… Mechanical Energy Thermal Energy Chemical Energy Electrical Energy Electromagnetic Energy Nuclear Energy

Forms of Energy Each form of energy can be converted into other forms of energy Energy can be neither created or destroyed

Mechanical Energy Mechanical energy is the energy associated with the motion and position of everyday objects Mechanical energy = the potential energy + the kinetic energy

Mechanical Energy Examples:

Thermal Energy Thermal Energy is the total potential and kinetic energy of an object due to movement in microscopic particles As the microscopic particles in an object speed up, thermal energy increases and the object become warmer

Thermal Energy Examples:

Chemical Energy Chemical energy is the energy stored in chemical bonds When the chemical bonds are broken, energy is released All chemical compounds store energy

Chemical Energy Examples: Gasoline stores chemical energy. When gasoline is burned, some chemical energy is released and converted into mechanical energy to move a car

Chemical Energy Chemical energy can also be released within your body Chemical reactions break down food which gives you energy

Electrical Energy Electrical energy is the energy associated with electrical charges Electric charges can exert forces that do work Electrical Energy can also occur in nature

Electrical Energy Examples:

Electromagnetic Energy Electromagnetic energy is a form of energy that travels through space in the form of waves Visible light and x-rays are examples of electromagnetic energy

Electromagnetic Energy Examples:

Nuclear Energy The energy stored in the nucleuses of atoms is called nuclear energy Nuclear energy is released by the fusion (combining) or fission (splitting) of atoms

Nuclear Energy Examples: