**Topic:**

Introduction to Physical Science B!

**Unit:**

7

**Objectives:**

- The students will be able to calculate work, force, and distance using the formula Work=Force X Distance;
- The students will be able to calculate power, work, and time using the formula Power=Work/Time;
- The students will be able to explain the relationship between Work & Power.

**Prior Knowledge: **

The students should have prior knowledge of:

- formula: Weight (newtons) = Mass x Acceleration due to gravity
- Mass (kg) = Weight(lbs)/2.2
- Definitions: Force, Weight, Distance, Time, Gravity
- Units: Acceleration due to gravity on Earth (9.8 N/kg), Weight (newtons), Mass (kg), Distance (meters), Time (seconds)

**Course Digital Resources:**

Link -> Mr. Tyler’s Physical Science Digital Resources

**Guiding Questions: **

- What is work?
- What happens to work when distance equals zero?
- What happened to the amount of work done after you climbed the stairs twice, each time at a different speed?
- How do you determine your weight in newtons?
- What is power?
- Why does power have a time unit?
- Can you use more than one formula to find “work”?
- How are work and power related?

**Agenda:**

**Task #1**

- I will be putting these definitions and formulas of work and power on the smart board/board:
- Work – The transfer of energy that results from applying a force over a distance
- Work = Force X Distance
- Power – The rate of doing work.
- Power = Work/Time

### Assignment** #1**

**SAMPLE QUESTIONS: **

Sample problem 1:

A person pushes a shopping cart with a force of 9.0 newtons in a straight line for 12 meters. How much work was done?

- Answer:

Sample problem 2 :

If the person in the previous question pushed the cart for 6.0 seconds, how much power was generated?

- Answer:

Sample problem 3: How far can you push a sled if you exert a force of 7.0 newtons in the same direction, and the amount of work on it is 56 joules?

- Answer:

Sample problem 4: How much time did it take a person that did 50 joules of work pushing a box to generate 10 watts of power?

- Answer:

Sample Problem 5:

How much power is generated by a 60.kg person climbing a flight of stairs 15. meters high for 5.0 seconds?

- Answer:

**Assignment #2**

**Guided Practice: **

You will answer 5 work and power word problems using work and power equations.

- How much work does an elephant do while moving a wagon 40 meters with a pulling force of 400N?
- If it takes 15 seconds for you to do 3000 J of work, what is your power output?
- A 900 N mountain climber scales a 200 m cliff. How much work is done by the mountain climber?
- A small motor does 8000 J of work in 20 seconds. What is the power of the motor in watts?
- A woman runs a kilometer using a force of 250 N and a power output of 500 W. How long in minutes does it take this woman to complete 1 kilometer?

**Assignment #3**

**Power Climb Lab **

DOWNLOAD – .doc Lab -> physical science – power climb lab

- Each student will be handed a worksheet with instructions to complete the activity.
- The students will be: calculating weight(force) of person climbing the stairs, measuring the vertical distance of the flight of stairs, calculating work, calculating power and sharing the results on the board.
- We will have an oral discussion (guided questions)

##### Special Materials Needed for Lab:

- 1 flight of stairs/bleachers (5 yards distance between groups)
- metric ruler
- stopwatches
- bathroom scale (lbs)
- calculator

### Assignment #3

### Summative Assessment

Each student will complete a 10 question written assignment related to work and power:

- What is the work formula equation that you used in class today?
- What is the power formula equation that you used in class today?
- John uses 50 N of force to push a shopping cart 10 meters. How much work does he do in joules?
- Liz does 4800. J of work in climbing a set of stairs. If she does the work in 6.00 seconds, what is her power output?
- How much work is required to pull a sled in order to generate 30 W of power for 5 seconds?
- 1 newton-meter is equal to 1 _______ of work.
- Power is usually measured in _______.
- How much work does a 50 kg person on Earth do if they lift up a barbell 2 meters above the ground?
- Thinking about the experiment you did in class today,
**EXPLAIN**why the amount of work**did not change**after climbing the stairs twice at different speeds? - Thinking about the experiment you did in class today,
**EXPLAIN**why the amount of power**did change**after climbing the stairs twice at different speeds?

DOWNLOAD – > summative assessment – power and work day – unit 7 – physical science

**Next Generation Science Standards:**

HS-PS 3-1 Create a computational model to calculate the change in the energy of one component in a system when the change in energy of the other components and energy flows in and out of the system are known.

HS-PS 3-3 Design, build and refine a device that works within given constraints to convert one form of energy to another form of energy.