Efficiency
Efficiency is the ratio of the amount of useful energy produced (energy output- Eout) to the amount of energy used (energy input- Ein), expressed as a percentage. Remember that no energy transforming device is 100% efficient:
Power
Power (P) is the word used to describe the rate at which work is done (or energy is transformed).Power may be confused by thinking that a more powerful machine does more work. This is not true. For example, if you have to people, one who does work in 5 seconds, and the other in 8 seconds but both do the same amount of work, which will more powerful? The answer is the one who does the same amount of work in less time, the shorter the time, the more powerful. Power can be caluclated using the following:
Like energy and work, power is also a scalar quantity, and it is measured in Watts (W= J/s).
Practice
Worksheets/Quizzes
1. http://www.physicsclassroom.com/calcpad/energy/problems.cfm (practice problems)
2. http://www.syvum.com/cgi/online/mult.cgi/squizzes/physics/work_energy.tdf?0 (practice problems)
3.http://www.nisd.net/taft/classrooms/martin/Assets/PDFWorksheets/WorkPowerMachines/images/EfficiencyProblems.pdf
(efficiency worksheet)
4.http://www.nisd.net/taft/classrooms/martin/Assets/PDFWorksheets/WorkPowerMachines/images/PowerWorkForce1.pdf
(practice problems)
5. http://www.softschools.com/quizzes/science/efficiency/quiz1698.html (efficiency-multiple choice quiz)
6. http://www.softschools.com/quizzes/science/power/quiz1697.html (power- multiple choice quiz)
7. http://www.physicsclassroom.com/class/energy/u5l1e.cfm (power- check your understanding- scroll down to bottom)
1. http://www.physicsclassroom.com/calcpad/energy/problems.cfm (practice problems)
2. http://www.syvum.com/cgi/online/mult.cgi/squizzes/physics/work_energy.tdf?0 (practice problems)
3.http://www.nisd.net/taft/classrooms/martin/Assets/PDFWorksheets/WorkPowerMachines/images/EfficiencyProblems.pdf
(efficiency worksheet)
4.http://www.nisd.net/taft/classrooms/martin/Assets/PDFWorksheets/WorkPowerMachines/images/PowerWorkForce1.pdf
(practice problems)
5. http://www.softschools.com/quizzes/science/efficiency/quiz1698.html (efficiency-multiple choice quiz)
6. http://www.softschools.com/quizzes/science/power/quiz1697.html (power- multiple choice quiz)
7. http://www.physicsclassroom.com/class/energy/u5l1e.cfm (power- check your understanding- scroll down to bottom)