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Power as the speed of doing work

Source: licencja: CC 0.

Moc jako szybkość wykonywania pracy

You will learn
  • You will learn how to developing analytical thinking in English.

Answer the introductory questions.

  1. How do we define work in physics?

  2. When is work done?

  3. Does work depend on the speed of doing work?

Conclusion:

  • The same work can be done in different time.

Power
Definition: Power
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nagranie abstraktu

PowerpowerPower is a physical quantity expressed numerically as the quotient of workworkwork and the time in which it was done:

power=workdonetime
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nagranie abstraktu

The formula is symbolically expressed as:

P=Wt

where:
P - powerpowerpower,
W - work done,
t - the time in which the workworkwork was done.

W (wat) is the unit of powerpowerpower:

[W]=[Js=Nms=kgmss2m=kgm2s3]
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nagranie abstraktu

PowerpowerPower provides information about:

  • what workworkwork was done in one second,

  • how quickly work was done.

Note:

If workworkwork is not being done uniformly, the above formula can be used to calculate the average powerpowerpower.

Task 1
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nagranie abstraktu

Open the applet and by moving the weight, check the powerpowerpower while doing workworkwork.

  1. Move the weight of the same mass over the same distance in a very long time and a very short time.

  2. Move the weights of different masses over the same distance at the same time. In which case are you working with more powerpowerpower?

  3. What value of powerpowerpower is displayed in the applet window?

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Geogebra aplet - Moc. Galeria z opisami alternatywnymi poniżej.
Power
Source: GroMar, licencja: CC BY 3.0.
Task 2
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nagranie abstraktu

What does it mean that one device has more power thanmore power thanmore power than the other one? Think about two possible cases.

Task 3
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nagranie abstraktu

A strongman lifted a barbell weight of 1500 N to the height of 2 m.

  1. What workworkwork did the strongman do?

  2. What powerpowerpower did he work with, if he raised the barbell in 10 seconds?

Exercise 1
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nagranie abstraktu

The maximum engine powerpowerpower of a passenger car is 40 kW, while the truck is powered by a motor with a maximum power of 240000 W. While driving uphill, the engines of both cars work with full powerpowerpower. The car engine did workworkwork (W) in 60 seconds.

  1. The truck engine did the same work during ... seconds.

  2. After 2 minutes of workworkwork, the truck engine did the work ... times greater than the passenger car engine.

Exercises

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Exercise 2
Goods were brought to a store. To unload the car, the work of 4 MJ is required. It is possible to transport the goods from the car to the store in the shortest possible time, when the work is done:
1. only by the driver with the power of 0,5 kilowatts - 1. over 45 minutes, 2. over 47 minutes, 3. over 133 minutes, 4. over 17 minutes, 5. over 18 minutes, 6. over 131 minutes,
2. two workers with the total power of 1,5 kilowatts - 1. over 45 minutes, 2. over 47 minutes, 3. over 133 minutes, 4. over 17 minutes, 5. over 18 minutes, 6. over 131 minutes,
3. a forklift with the power of 4 kilowatts - 1. over 45 minutes, 2. over 47 minutes, 3. over 133 minutes, 4. over 17 minutes, 5. over 18 minutes, 6. over 131 minutes.
Exercise 3

While skating for 2 seconds, Piotr was pushing off the ice with the horizontal force of 200 N. During this time, he covered the distance of 10 m only.

  1. What was his power and how much work did he do in 1 second?

  2. By how many meters did Piotr move in 1 second? Remember that he was moving in uniform motion.

Exercise 4

The power output of an electric motor is 2 kW. The motor must lift 2000 N to the height of 4 m with an electric winch. On the basis of the situation presented above, formulate two computational tasks in English.

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Exercise 5
Wersja alternatywna ćwiczenia: Indicate which pairs of expressions or words are translated correctly. Możliwe odpowiedzi: 1. moc urządzenia - device power, 2. równe moce - equal powers, 3. czas wykonania pracy - time of work, 4. szybkość wykonywania pracy - work speed, 5. mniejsza moc niż - more power than, 6. większa moc niż - less power than
zadanie
Source: GroMar, licencja: CC BY 3.0.
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Interaktywna gra, polegająca na łączeniu wyrazów w pary w ciągu jednej minuty. Czas zaczyna upływać wraz z rozpoczęciem gry. Jeden ruch to odkrywanie najpierw jednej potem drugiej karty z wyrazem. Każdy wyraz jest odczytywany. Kolejny ruch to odkrywanie trzeciej i czwartej karty. W ten sposób odsłuchasz wszystkie wyrazy. Nawigacja z poziomu klawiatury za pomocą strzałek, odsłuchiwanie wyrazów enterem lub spacją. Znajdź wszystkie pary wyrazów.
Source: Zespół autorski Politechniki Łódzkiej, licencja: CC BY 3.0.

Glossary

device power
device power

moc urządzenia

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wymowa w języku angielskim: device power
equal powers
equal powers

równe moce

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wymowa w języku angielskim: equal powers
in shorter time
in shorter time

w krótszym czasie

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wymowa w języku angielskim: in shorter time
less power than
less power than

mniejsza moc niż

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wymowa w języku angielskim: less power than
more power than
more power than

większa moc niż

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wymowa w języku angielskim: more power than
power
power

moc

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wymowa w języku angielskim: power
time of work
time of work

czas wykonania pracy

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wymowa w języku angielskim: time of work
work
work

praca

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wymowa w języku angielskim: work
work speed
work speed

szybkość wykonywania pracy

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wymowa w języku angielskim: work speed

Keywords

powerpowerpower

time of worktime of worktime of work

work speedwork speedwork speed

workworkwork