Unit 7 - Lesson 1: Work & Power

Unit 7
Power & Energy
(Ch 4 & Ch 5)

TEKS Covered this Unit:

1E: collect quantitative data using the SI units and qualitative data as evidence
1F: organize quantitative and qualitative data using labeled drawings and diagrams, graphic organizers, charts, tables, and graphs
4A: analyze, evaluate, and critique scientific explanations and solutions by using empirical evidence, logical reasoning, and experimental and observational testing, so as to encourage critical thinking by the student
6C: plan and conduct an investigation to provide evidence that energy is conserved within a closed system
6G: evaluate evidence from multiple sources to critique the advantages and disadvantages of various renewable and nonrenewable energy sources and their impact on society and the environment

Vocabulary

• energy – the ability to do work

•  power – the amount of work that is applied to an object in one second

•  work – the transfer of energy that takes place when a force causes an object to move

In order for work to be applied:
1. Work requires motion
- object has to actually MOVE
2. Force and motion of an object must be in the same direction

Two conditions:

transfer of energy that takes place when a force causes an object to move

What is WORK?

1) Energy is the ability to do work

2) When work is done on an object, the energy of the object increases

3) Work is essentially a transfer of energy

There is always a transfer of energy that takes place when work is done on an object

Work & Energy

CALCULATING WORK

Example:

A woman exerts a 75 N force on a dolly that is holding several moving boxes. If she moves the dolly 15 m, how much work was a pplied to the dolly (and boxes)

Fill in the Blanks

You move a 25 N object 5 meters. How much work did you do?

• Power - the amount of work applied to an object in one second

• Think of power as a type of rate - a rate at which work is performed

It's All POWER

Power (watts) 

Work (joules)

Or Energy (joules)
Time (seconds)

POWER

Example:

You enter into a competition with your friend to determine who can push a heavy box the fastest in a certain period of time. It took your 7 seconds to push a 50 N box for a distance of 4 m. How much power did you exert while performing work on the box?

Fill in the Blanks

You do 45 J of work in 3 seconds. How much power do you use?

Poll

How good do you feel about today's lesson?

• 1 - LOST

• 2 - STRUGGLING

• 3 - GETTING THERE

• 4 - GOT IT