4Energy-3
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Revision as of 07:40, 18 February 2012 by Mrsaunders (Talk | contribs) (New page: ==Outcomes== * Pupils can recall the Law of the Conservation of Energy. * Pupils understand how the conservation of energy applies in real-life contexts. * Pup...)
Contents
Outcomes
- Pupils can recall the Law of the Conservation of Energy.
- Pupils understand how the conservation of energy applies in real-life contexts.
- Pupils understand the idea of efficiency and can calculate the efficiency of of energy transfers.
Specification References
4.3 understand that energy is conserved
4.4 recall and use the relationship: Efficiency = useful energy output/total energy input
Starter
- Select a pupil and demonstrate that a heavy pendulum bob released from the tip of their nose never returns far enough to strike them.
Main Body of Lesson
- Following on from the starter elicit the idea that in the pendulum system there is a constant back-and-forth transfer between GPE-kinetic-GPE but that during each swing some kinetic energy is lost as thermal energy due to friction (elicit "air resistance" as a type of friction).
- Move on to discussing bouncy balls. Ask pupils how they would measure the "bouncyness" of a ball.
- Elicit the energy transfer as gravitational potential to kinetic to elastic potential to kinetic to gravitational potential.
- Pupils carry out experiment to find the efficiency of the return of energy of a bounce, they could also find the coefficient of restitution of bouncy ball.
- Discuss results of bouncy ball experiment. Elicit the idea that the bouncy ball loses a "fixed" percentage of its kinetic energy each time, resulting in a graph that is curved.
- Suggestion: Compiling all pupil results into one spreadsheet and averaging out produces a very good exponential curve.
Practicals/Demonstrations
- Conservation of energy demonstration using volunteer pupil and large pendulum.
Finding the coefficient of resitution of a bouncy ball
- Each group has one bouncy ball and a metre rule.
- Pupils measure the maximum height a bouncy ball reaches after being dropped onto a hard surface (e.g. laboratory floor) from a height of one metre.
- Pupils then drop the ball again from the previous height reached. By doing the experiment this way they find the height of each bounce in a series without having to do it all at once.
Plenary
- Discuss the energy transfers involved; this is an excellent opportunity to begin considering energy "losses" in a more rigourous manner.
Homework
Additional Information
Resources Required
- Large heavy pendulum suspended from ceiling.
- Bouncy balls (1 per group)
- Metre rules
Skills Addressed
- Understanding conserved quantities.
Safety/Hazards
- Ensure that pupil remains absolutely stationary during pendulum demonstration to avoid the bob striking them.