Topicm420ecb136f17f16c_1528449000663_0Topic

PowerpowerPower as the time of doing workworkwork

Levelm420ecb136f17f16c_1528449084556_0Level

Second

Core curriculumm420ecb136f17f16c_1528449076687_0Core curriculum

III. Energy. The student:

1) uses the definition of powerpowerpower and its unit; applies the relationship between power, work and time of doing workworkwork in calculations.

Timingm420ecb136f17f16c_1528449068082_0Timing

45 minutes

General learning objectivesm420ecb136f17f16c_1528449523725_0General learning objectives

Developing analytical thinking.

Key competencesm420ecb136f17f16c_1528449552113_0Key competences

1. Developing the ability to define physical quantity.

2. Introduction to the definition of powerpowerpower.

3. Using the definition of power in typical situations.

Operational (detailed) goalsm420ecb136f17f16c_1528450430307_0Operational (detailed) goals

The student:

- defines the notion of power,

- calculates powerpowerpower in common situations.

Methodsm420ecb136f17f16c_1528449534267_0Methods

1. Learning through observation.

2. Learning through the application the acquired formulas.

Forms of workm420ecb136f17f16c_1528449514617_0Forms of work

1. Individual workworkwork.

2. Group work.

Lesson stages

Introductionm420ecb136f17f16c_1528450127855_0Introduction

How do we define workworkwork in physics?

When is work done?

Does work depend on the speed of doing work?

Conclusion:

The same workworkwork can be done in different time.

Procedurem420ecb136f17f16c_1528446435040_0Procedure

Definition:

Power is a physical quantity expressed numerically as the quotient of work and the time in which it was done:m420ecb136f17f16c_1527752263647_0Power is a physical quantity expressed numerically as the quotient of work and the time in which it was done:

The formula is symbolically expressed as:m420ecb136f17f16c_1527752256679_0The formula is symbolically expressed as:

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

W (wat) is the unit of power:m420ecb136f17f16c_1527752256679_0where:
P - power,
W - work done,
t - time in which the work was done.

W (wat) is the unit of power:

PowerpowerPower provides information about:
- what work was done in one second,
- how quickly workworkwork was done.

Note:
If work is not being done uniformly, the above formula can be used to calculate the average power.

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

[Geogebra applet]

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

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

Task
A strongman lifted a barbell with weights of 1500 N to the height of 2 m.
1) What work did the strongman do?
2) What powerpowerpower did he workworkwork with, if he raised the barbell in 10 seconds?

Task
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 workworkwork with full powerpowerpower. The car engine did work (W) in 60 seconds.
1) The truck engine did the same work during ... seconds.
2) After 2 minutes of work, the truck engine did the workworkwork ... times greater than the passenger car engine.

Answer:
1) 10 s,
2) 6 times.

Lesson summarym420ecb136f17f16c_1528450119332_0Lesson summary

Power is the quotient of work done by a device or a person and the time in which the work was done.
One device works with more power than the other when:
1) it does greater work at the same time,
2) does the same work in shorter time.m420ecb136f17f16c_1527712094602_0Power is the quotient of work done by a device or a person and the time in which the work was done.
One device works with more power than the other when:
1) it does greater work at the same time,
2) does the same work in shorter time.

Selected words and expressions used in the lesson plan

device powerdevice powerdevice power

equal powersequal powersequal powers

in shorter timein shorter timein shorter time

less power thanless power thanless power than

more power thanmore power thanmore power than

powerpowerpower

time of worktime of worktime of work

workworkwork

work speedwork speedwork speed