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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 • • Chemical • • _________________ atoms and ions together. Electromagnetic (electrical) • • internal __________________of particles. _____________________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 KE = ½mv2 Equation: 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?
