ppt power
TRANSCRIPT
![Page 1: Ppt Power](https://reader034.vdocuments.site/reader034/viewer/2022052619/5563b92ed8b42a79028b53df/html5/thumbnails/1.jpg)
POWER
![Page 2: Ppt Power](https://reader034.vdocuments.site/reader034/viewer/2022052619/5563b92ed8b42a79028b53df/html5/thumbnails/2.jpg)
Power
• Suppose you and a friend are pushing boxes of books up a ramp and into a van.
• Each box is the same weight. • You make a game…who can push
the box up faster?
![Page 3: Ppt Power](https://reader034.vdocuments.site/reader034/viewer/2022052619/5563b92ed8b42a79028b53df/html5/thumbnails/3.jpg)
Power
• The friend moves the box up faster than you. She does it in 30s you do it in 45s.
• You both do the same amount of work.• Why? How does this happen? She’s
faster.• She was faster, and had more power,
but you did the same amount of work.
![Page 4: Ppt Power](https://reader034.vdocuments.site/reader034/viewer/2022052619/5563b92ed8b42a79028b53df/html5/thumbnails/4.jpg)
Power
• Power is the amount of work done in a certain amount of time.
• Power is a rate – • The rate at which work is done.
• Power = Work/time• P = W/t
![Page 5: Ppt Power](https://reader034.vdocuments.site/reader034/viewer/2022052619/5563b92ed8b42a79028b53df/html5/thumbnails/5.jpg)
Power
• It took 20 minutes (1,200 sec) to move a box. You did 40,000 Joules of work in the process. How much power did you use?
• t = 20min = 1,200 sec
• W = 40,000 J• P = ?
•Remember = Joules / second = Watt
•Power is always measured in Watts
•P = W/t
•P = 40,000 J/1,200 sec•P = 33.33 J/sec
•P = 33.33 W
![Page 6: Ppt Power](https://reader034.vdocuments.site/reader034/viewer/2022052619/5563b92ed8b42a79028b53df/html5/thumbnails/6.jpg)
Calculating Power
• Power is measured in – Watts (W)
• The watt is named after James Watt. He helped to develop the steam engine.
• A watt (W) is 1 J/s• A watt is a pretty small unit.
![Page 7: Ppt Power](https://reader034.vdocuments.site/reader034/viewer/2022052619/5563b92ed8b42a79028b53df/html5/thumbnails/7.jpg)
Calculating Power
• Large amounts of watts are usually shown in kilowatts.
• One kilowatt (kW) is equal to how many watts?
• 1,000 W • If you were to run up one flight of stairs
it would use about 1 kW of power.
![Page 8: Ppt Power](https://reader034.vdocuments.site/reader034/viewer/2022052619/5563b92ed8b42a79028b53df/html5/thumbnails/8.jpg)
Power & Energy
• Doing work transfers energy from one object to another.
• Energy can be transferred in other ways that don’t involve something moving.
• Lightbulbs…
![Page 9: Ppt Power](https://reader034.vdocuments.site/reader034/viewer/2022052619/5563b92ed8b42a79028b53df/html5/thumbnails/9.jpg)
Power & Energy
• A lightbulb uses electrical energy to produce heat and light…but no work is done.
• Power is made or used any time energy is transferred divided by the time needed for the transfer to happen.
• Anytime energy is transferred from one object to another, power can be calculated.
• Power = Energy/time• P=E/t
![Page 10: Ppt Power](https://reader034.vdocuments.site/reader034/viewer/2022052619/5563b92ed8b42a79028b53df/html5/thumbnails/10.jpg)
Changing Energy by Doing Work
• What happens to the energy of the book when you lift it off your desk?
• You changed the height of the book so it changed the potential energy.
• Where did this increase of energy come from?
• You transferred energy to the book by lifting it up.
![Page 11: Ppt Power](https://reader034.vdocuments.site/reader034/viewer/2022052619/5563b92ed8b42a79028b53df/html5/thumbnails/11.jpg)
Changing Energy by Doing Work
• You can also increase the kinetic energy of something by doing work on it.
• For example, pushing a chair…• When you push a chair, you do work
on it and it now has kinetic energy.
![Page 12: Ppt Power](https://reader034.vdocuments.site/reader034/viewer/2022052619/5563b92ed8b42a79028b53df/html5/thumbnails/12.jpg)
Changing Energy by Doing Work
• Rub your two hands together. What happens?
• They feel warm.• Why? • The energy of your hands increased
in the form of heat caused by friction. • Anytime you do work on an object,
you cause its energy to increase.