Chapter 13 Energy & Power How is energy important to us?

Energy The ability to do work or cause change is called energy. Works is the transfer of energy. Two types of energy : – Kinetic energy is energy of motion. – Potential energy is energy of position or shape.

Kinetic Energy Kinetic energy = mass x (velocity) 2 /2 Doubling the mass, doubles the kinetic energy. Double the velocity, quadruple the kinetic energy.

Potential Energy Elastic potential energy is energy stored when an object is stretched or compressed. Gravitational potential energy is energy stored because of the height of the object’s position. Gravitational potential energy = weight x height. Energy is measured in units called Joules.

Forms of Energy Mechanical energy is the energy associated with the motion or position of an object. Thermal energy is the total energy of the particles in an object. Chemical energy is the potential energy stored in chemical bonds that hold chemical compounds together.

Forms of Energy Electrical energy is moving electric charges produce electricity and energy. Electromagnetic energy travels in waves and have both electrical & magnetic properties. Nuclear energy is energy stored in the nucleus of an atom and is released during nuclear reactions.

In which units do we measure energy? 1. gram 2. joule 3. kilogram 4. Newton

When you wind up a rubber band on an airplane, what type of energy does this represent? 1. Chemical potential energy 2. Elastic potential energy 3. Gravitational potential energy 4. Kinetic energy

Which type of energy travels in waves? 1. Electrical 2. Electromagnetic 3. Mechanical 4. Nuclear

Energy Conversion and Conservation A change from one form of energy to another is called energy conversion. Most forms of energy can be converted into any other form. What is the energy conversion of the flashlight in the diagram on the right?

Energy Conversion What is the energy conversion for the fan in the diagram on the right?

Conservation of Energy Law of conservation of energy states that when one form of energy is converted to another, no energy is destroyed in the process. According to the law of conservation of energy, energy cannot be created or destroyed.

Fossil Fuels Fossil fuels are formed from the burying of plants and animals. Include coal, petroleum and natural gas. Fossil fuels contain energy that came from the sun. Fossil fuels can be burned to release the potential chemical energy stored millions of years ago.

Power Power is the rate at which work is done or the amount of work done in a unit of time. Power is calculated by dividing the amount of work done by the amount of time taken to do work. – Power = work/time – Power = force x distance/time – Power is measured in watts.

Power (continue) Power is the rate at which energy is transferred form one object to another or converted from one form to another. One horsepower is equal to 746 watts.

Pendulum Lab Purpose: The purpose of this lab is for the students to learn which factor affects the period of the swing of a pendulum. Materials: – 3 different weights – meter stick – string – stopwatch – ring stand

Pendulum Lab Procedure: 1. Tie a weight to the end of a string. 2. Attached the other end of the string to the ring stand. 3. Pull the weight back a standard distance and release the weight. 4. Time how long it takes for ten cycles of the pendulum. Enter this data on the data table.

Pendulum Lab 5. Divide the time by ten to find the time for a single swing. 6. Change the weight and repeat procedures Change the weight and repeat procedures Next change the length of the string and keep the weight the same. Repeat procedures 1-5.

Pendulum Lab 9. Change the length of the string a second time and keep the weight the same. Repeat procedures Change the angle of release. Repeat procedures Change the angle of release. Repeat procedures 1-5.

Pendulum Lab Questions: 1. Make a drawing of the pendulum. Indicate on the diagram the positions of the maximum potential energy and the maximum kinetic energy. 2. What were the variables in this experiment? Which was the manipulative variable and which was the responding variable? 3. Explain how the Law of the Conservation of Energy is observed in this experiment. 4. What forces act on the pendulum to stop its motion?

Pendulum Lab Look at the diagram on the right.

Formative Assessment Review What are the two types of energy? (kinetic and potential) Which type of energy is energy of motion? (kinetic) Which type of energy is stored energy? (potential) Which type of energy is stored in a stretched rubberband or compressed spring? (elastic potential energy) Which type of energy is stored because of the position of the object? (gravitational potential energy)

Formative Assessment Review What is the formula for calculating kinetic energy? (KE=mv2/2) What is the formula for calculating gravitational potential energy? (GPE=w x h or GPE=m x g x h) Name six forms of energy. (mechanical, thermal, chemical, electrical, electromagnetic, nuclear) Which law states that energy is neither created or destroyed? (Law of Conservation of Energy) What is the formula for calculating Power? (P=w/t)

Formative Assessment Review What unit is power measured? (watt) What unit is work or energy measured? (joule) What do we call the ability to do work or cause change? (energy) What happens to kinetic energy if the mass is doubled? (doubles) What happens to kinetic energy if the velocity doubles? (quadruples) _______________ is the transfer of energy. (work)

Formative Assessment Review What is the numerical value of gravitational acceleration? (9.8 m/s2) What energy is associated with motion or position? (mechanical) What energy is associated with the total energy of the particles of an object? (thermal) What energy is associated with the potential energy stored in chemical bonds? (chemical) What energy is produced by moving electric charges? (electrical)

Formative Assessment Review What energy travels in waves? (electromagnetic) What energy is stored in the nucleus of an atom? (nuclear) What is it called when an energy form changes to another form of energy? (converstions) Who stated that energy can be created by destroying matter? (Einstein) How is energy released from fossil fuel? (burning)

Formative Assessment Review What energy is mechanical energy converted to by friction? (thermal) Name three fossil fuels. (coal, petroleum, natural gas) _______________ is the rate at which work is done. (power) How many watts are in one horsepower? (746)