Embed Size (px)
Citation preview
Energy Work and Power Lesson Revised 2016.notebook
1
December 01, 2016
Energy (Forms and Conservation), Work & Power
Energy Work and Power Lesson Revised 2016.notebook
2
December 01, 2016
Energy Work and Power Lesson Revised 2016.notebook
3
December 01, 2016
Phet Simulation Energy Skate Park
Energy Work and Power Lesson Revised 2016.notebook
4
December 01, 2016
Energy a quantity that measures the ability to change or move matter
unit Joules or Newton meter (1 J = 1 N m) scalar
Approximation: 1 J of energy could lift 1 apple (1 N) a distance of 1 meter.
2 Categories of Energy
Mechanical Energy (ME) energy that can easily be transferred to move or change the matter.
ex: Kinetic and Potential.
Non mechanical Energy (NME) energy that can not easily be transferred to move or change the matter.
ex: Heat & Sound
Energy Work and Power Lesson Revised 2016.notebook
5
December 01, 2016
Mechanical Energy
Energy Work and Power Lesson Revised 2016.notebook
6
December 01, 2016
Energy Work and Power Lesson Revised 2016.notebook
7
December 01, 2016
Energy Work and Power Lesson Revised 2016.notebook
8
December 01, 2016
Non Mechanical Energy
Energy that can not easily change or move matter
Heat and Sound
Energy Work and Power Lesson Revised 2016.notebook
9
December 01, 2016
• Unit = Joule = Newton meter• 1 Joule of work is done when 1 N acts on a body moving it a distance of
1 meter
Energy Work and Power Lesson Revised 2016.notebook
10
December 01, 2016
Energy Work and Power Lesson Revised 2016.notebook
11
December 01, 2016
• Work changes mechanical energy!
• If an applied force does positive work on a system, it tries to increase mechanical energy.
• If an applied force does negative work, it tries to decrease mechanical energy.
• The two forms of mechanical energy are called potential and kinetic energy.
Work and Energy
• If a system does work on the surroundings the total energy of the system decreases
Energy Work and Power Lesson Revised 2016.notebook
12
December 01, 2016
The WorkEnergy Theorem• The net work due to all forces acting on a system equals the change in the energy of a system.
• Wnet = ∆Ε
> Wnet: work due to all forces acting on an object.> ∆Ε: change in energy (Ef – Ei)
> This corresponds to our energy diagram from the beginning of the lesson.
– The change in the energy of the Biff, Balloon, Earth system was equal to the work added by Buffy.
Energy Work and Power Lesson Revised 2016.notebook
13
December 01, 2016
Summary: Type of Energy and Work
TE TE = ME + NME Everything put togetherTotal Energy
Work W W = F d cos θ The force of gravity pulling an object down
Type Symbol Equation Example
Kinetic Energy K K= 1/2 mv2 a ball rolling
Gravitational Potential Energy Ug Ug = mgh an acorn above the ground
Elastic Potential Energy Us Us = 1/2 k x2 compressed spring
Mechanical Energy ME ME = K+ U a bird flying
Nonmechanical Energy NME NME= Wnc Heat and Sound
Energy Work and Power Lesson Revised 2016.notebook
14
December 01, 2016
Constant force and work• The force shown is a constant force.• W = Fd can be used to calculate the work done by this force when it
moves an object from xa to xb.• The area under the curve from xa to xb can also be used to calculate
the work done by the force when it moves an object from xa to xb
Energy Work and Power Lesson Revised 2016.notebook
15
December 01, 2016
Energy Work and Power Lesson Revised 2016.notebook
16
December 01, 2016
Energy Work and Power Lesson Revised 2016.notebook
17
December 01, 2016
Unit of Power• SI unit for Power is the Watt.
> 1 Watt = 1 Joule/s> Named after the Scottish engineer James Watt
(17761819) who perfected the steam engine.• British system
> horsepower> 1 hp = 746 W
Energy Work and Power Lesson Revised 2016.notebook
18
December 01, 2016
Total Energy initial = Total Energy final = Total energy at any position or time = Constant
TEi = TEf = TEanywhere/anytime = Constant
Energy Work and Power Lesson Revised 2016.notebook
19
December 01, 2016
Steps to solve energy problems:
1. Read carefully, identify givens and draw a picture
2. Determine types of energy involved at different positions/times (Initial vs Final)
3. Set up a conservation equation (include NME if necessary)
TEA = TEB
4. Solve for missing quantity. (speed, height, stretch, etc)
Energy Work and Power Lesson Revised 2016.notebook
20
December 01, 2016
Energy Work and Power Lesson Revised 2016.notebook
21
December 01, 2016
Energy Work and Power Lesson Revised 2016.notebook
22
December 01, 2016
Energy Work and Power Lesson Revised 2016.notebook
23
December 01, 2016
Energy Work and Power Lesson Revised 2016.notebook
24
December 01, 2016
