Difference between revisions of "3-NRG-02"
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* Pupils understand how the conservation of energy applies in real-life contexts. | * Pupils understand how the conservation of energy applies in real-life contexts. | ||
==[[Specifications|Specification]] References== | ==[[Specifications|Specification]] References== | ||
| − | + | 4.3 understand that energy is conserved | |
| + | |||
==Starter== | ==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. | * Select a pupil and demonstrate that a heavy pendulum bob released from the tip of their nose never returns far enough to strike them. | ||
Revision as of 13:36, 16 February 2010
Contents
Outcomes
- Pupils can recall the Law of the Conservation of Energy.
- Pupils understand how the conservation of energy applies in real-life contexts.
Specification References
4.3 understand that energy is conserved
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 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.
- Pupils carry out experiment to investigate the effect of temperature on the coefficient of restitution of a squash ball.
- Discuss results of squash ball experiment. Elicit the idea that the heated balls bounce higher (have a higher coefficient of restitution) than the cooler ones. Pupils may notice that for different balls the difference between hot and cold is different - there is no fixed relationship that applies to balls of different colour.
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.
Comparing squash balls
- Each group has three squash balls of each colour.
- One ball of each colour should be made hot, one cold, and one kept at room temperature.
- Pupils drop each ball from a height of one metre and record the height they reach on their first bounce.
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
- Squash balls (3 of each colour per group (with sharing between groups 12 each of four colours works well))
- Spreadsheet with example results and graphs (SST001)
Skills Addressed
- Understanding conserved quantities.
Safety/Hazards
- Ensure that pupil remains absolutely stationary during pendulum demonstration to avoid the bob striking them.
