Energy, Work, PowerChapter 7

Know what you need...

• Look through your syllabus to guide you in your learning.

• Where can you find these information from the textbook?

• Are you able to answer short questions from your textbook?

• Construct mind maps to consolidate ideas/ Handbook for each topic.

Energy

• What is energy?– Is the capacity to do work

• SI unit for energy is Joule (J).• Energy that relates to motion are:– Kinetic energy– Potential energy

• Principle of energy conservation– Energy cannot be created or destroyed

but only changes from one form to another.

Kinetic Energy

• What is kinetic energy?– Energy that the object has due to its motion.

• Factors affecting K.E– Mass– Speed– KE = ½ mv2

• Potential energy can be converted to kinetic energy. (vice versa)

• K.E can also be converted to other forms of energy. E.g. Kinetic Torch light: K.E. convert to chemical potiential energy

Potential Energy

• What is potential energy?– It is stored energy in an object due to its position

or state.

• What does conservation of energy state about an object that falls from a certain height?– Potential energy is converted to Kinetic energy

• Factors affecting Gravitational P.E:– Mass– Gravitational field strength– Height– G.P.E. = mgh

Types of Energy

Main types:• Potential energy– Chemical– Gravitational– Elastic

• Kinetic energy– Thermal energy– Sound energy– Electrical energy– Wave energy

Calculation

• Understand the LAW of conservation of energy!

• Memories your formulae.• Combine the two to understand the question.• List down the information you have and its

units.• Finally answer the question!

Practice: Textbook, Workbook, TYS

Homework

• Read up on chapter 7.3 & 7.4• When is work considered done?• How is it calculated?• What is the SI unit for work done?• Give examples of work not done.• What is power?• What is the SI unit for power?• How is it calculated?