work

·         4.16 understand the energy transfers involved in generating electricity using:

·         wind

·         water

·         geothermal resources

·         solar heating systems

·         solar cells

·         fossil fuels

·         nuclear power

wind energy story.swf Download this file

Teacher Presentation.ppt Download this file

DragnDropEnergy.swf Download this file

Starter.ppt Download this file

advantages and disadvantages of energy resources

Power questions

Power questions

19 August 2011

17:30

PFY, p. 120

F) power is the rate of doing work

     power (in watts) = work done (in seconds)/ time (in seconds)

G) 1 watt is a rate of working of one joule per second

13. P = E/t = 1000/5 = 200w

14. Wd = Fx d = 300 x 2 = 600J     P= E/r = 600/6 = 600J

16. Wd = Fxd = 300 x 10 = 30,000J   P= E/t = 30000/4 = 7500

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CoE questions

PFY p.121

 19 a) 50 x 10= 500N

  b) gpe = mgh = 10 x 50 x 4 = 2000J

Collins, p.91

3 a) gpe = mgh = 35 x 10 x 10,500J

   b) gpe at top = KE at bottom

       KE = .5m v2 = 10,500 = .5 x 35 x v2

       v2 = 600

       v = 24.5m/s

   c) not all of the gpe is transferred to KE, some energy is wasted due to friction

4.13

·         

4.13 understand how conservation of energy produces a link between gravitational potential energy, kinetic energy and work

CoE.ppt Download this file

4.10

4.10

10 June 2011

11:51

PFY p.112

·         

4.10 understand that work done is equal to energy transferred

      A) The work done (measured in Joules) is equal to the force 

     (in newtons) multiplied by the distance moved (in meters)

B) 1 joule is the work done when a force of one newton moves 

    through a distance of one meter (in the direction  of the force)

C) work done = energy transferred

WD= Fxd = 5x2= 10J

WD= Fxd = 500x40 = 20,00

the energy change is KE to GPE

4.9

4.9

10 June 2011

11:38

·         

4.9 recall and use the relationship between work, force and distance moved in the direction of the force:

       work done = force × distance moved         

Wd = F × d

Work formula.ppt Download this file

4B1 work done skiing downhill.swf Download this file

4B1 work done pushing a wheelbarrow.swf Download this file

Starter - answers

Starter - answers

19 August 2011

16:11

Tell the person next to you...

·         Imagine pushing a king sized bed from one side of the classroom to the other

·         Would it make you feel tired? 

o    Yup!

·         Would you have to work hard to push it?

o    Yup!

·         What could you change so you have to do less work pushing?

o    Anything that decreases the force needed (reduce friction by putting wheels on it, ice under it, etc)

o    Anything that decreases the distance travelled (only push it half way!, etc)

o    So the formula for work must contain forceand distance