Energy

Nature of Energy Energy is all around you! You can hear energy as sound. You can see energy as light. You can feel energy as wind. You use energy when you hit a ball Energy is involved when electricity flows in a wire

Living organisms need energy for growth and movement.

What Is Energy? Energy is the ability to do work. If an object or organism does work, the object or organism uses energy. Work is done if a force makes something move

6 Energy Types There are MANY types of energy 6 forms of energy are described below: Mechanical Energy: the energy of moving things Kinetic Energy: Energy of motion Potential Energy: stored energy

6 Energy Types (cont.) Electrical Energy: energy that flows through wires and powers lights and other appliances (the energy of moving charges) Electromagnetic Energy: the energy of visible light, X-rays, radio waves, microwaves, etc.

6 Energy Types (cont.) Heat Energy: also called thermal energy if you rub your hands, they become warm due to moving particles (atoms and molecules) of matter Chemical Energy: the energy that holds particles of matter together examples: energy stored in a match, food, fuels, etc.

6 Energy Types (cont.) Nuclear Energy: the energy stored in a nucleus of an atom can be released when atoms split or combine the heat and light from the Sun started as nuclear energy

What Is Energy Measured In? Joules (J) Same unit as work because the two are so closely related.

Vector or Scalar? Energy is a scalar This means that direction is NOT included

Mechanical Energy When work is done to an object, it acquires energy known as mechanical energy.

Mechanical Energy When you kick a football, you give mechanical energy to the football to make it move.

Mechanical Energy When you throw a bowling ball, you give it mechanical energy to make it roll.

Mechanical energy is made up of two energies: Kinetic energy Potential energy

Mechanical Energy Formula ME = KE + PE

Kinetic Energy Kinetic energy is the energy due to motion. Depends on both mass and velocity. The more mass an object has, the more kinetic energy. The faster an object moves, the more kinetic energy.

Kinetic Energy This bird has kinetic energy because it has mass and velocity.

Kinetic Energy

Kinetic Energy: Problem Solving

Kinetic Energy: Problem Solving

Potential Energy Potential Energy is due to an object’s position. Sometimes called “stored energy” The object now has the “potential” to do work on an object (it’s just not doing it now). Symbol: PE There are two kinds of potential energy: Gravitational Potential Energy Elastic Potential Energy

Gravitational Potential Energy PEg depends on height and mass. The greater the height, the greater the PEg. The greater the mass, the greater the PEg.

Gravitational Potential Energy A waterfall, a suspension bridge, and a falling snowflake all have gravitational potential energy because they are above the ground.

Gravitational Potential Energy PEg = mgh Where: m = mass (should be in kilograms) g = acceleration due to gravity = 10 m/s2 h = height (usually above the ground or floor) (should be in meters) PEg is usually measured in Joules (1 kgm2/s2 = 1 Nm = 1 Joule)

Gravitational PE: Alternate Formula PEg = m g h Notice that the formula has mg… Oh… what is mg??? mg = weight! Alternate formula: PEg = weight  height Remember: weight is measured in Newtons, mass is measured in kg

Gravitational Potential Energy If you stand on a 3 m diving board, you have 3 times the PEg you had on a 1 m diving board.

Elastic Potential Energy PEelastic depends on how much an object is being stretched or compressed.

Potential Energy: Problem Solving

Potential Energy: Problem Solving