Energy
•“Something” that enables an object to do ______– NOT a material substance!
•When you have “______” you can do work
•The amount of energy that an object has is related to the amount of ______the object can do.
•The amount of energy can be precisely ______.
•SI unit is Joules (J) – (N*m)
•Comes in various forms
Seven Main Forms of Energy
•Mechanical
•sum of ______energy in a system.
•______
•______
•Heat
•internal ______of particles.
•Chemical
•______atoms and ions together.
•Electromagnetic (electrical)
•______electric charges.
•Nuclear
•in the atomic nucleus.
•Nuclear ______& Nuclear______
Mechanical Energy
•Energy due to the position, or ______, of something
•Mass is, or will be, displaced
Nonmechanical Energy
•Mass is not displaced, no ______or velocity gained or lost
•Examples
•Chemical Energy
•Gasoline
•______
Potential Energy
•Potential Energy
•Energy an object has due ______
•______Energy
•Stored Work
•Examples
•Why do we not walk under ladders
•______
Gravitational Potential Energy
•due to ______acting on an object,
Equation: PE = mgh
______
Metric unit of energy is ______(same as for work).
Sample Problem
What is the potential energy of a 6kg bowling ball at a height of 20 meters?
Gravitational Potential energy is
PE = (mass) x (Gravity) x ( Height )
What is potential energy at zero height?
______
Kinetic Energy
•Energy associated with an object due to its ______.
•If something is in motion it has the ability to do ______
•A stationary object has zero kinetic energy
Equation: KE = ½mv2
KE= ½ x Mass x Speed2
Notice that speed is ______– a small increase in speed causes a large increase in kinetic energy!
Sample Problem
What is the kinetic energy of a 6kg bowling ball, falling from a height of 20 meters, just as it reaches the ground?
(Kinetic Energy) = ½ ( Mass ) x ( Speed ) x (Speed)
= ______
= ______
Conservation of Energy
•______states that energy can never be created or destroyed. It can only be transformed from one ______into another.
•Example
•A book falls from a table
•A ______
•The total Mechanical Energy must always be equal to the sum of Kinetic Energy and Potential Energy
Etotal = ______
Pendulum – Like a child on a swing
Energy exchange from PE to KE and back
Check for Knowledge
•Suppose you have a 1 kg mass at a height of 1.25 m. How much potential energy does it have?
•The mass is now let go. At the very bottom, what is it’s kinetic energy?
•What is the speed of the mass just before it hits the ground?