# Physical Science B SGI Lesson #7 (1-30-2019)

### Topic:

Introduction to Physical Science B!

7

### Objectives:

1. The students will be able to calculate work, force, and distance using the formula Work=Force X Distance;
2. The students will be able to calculate power, work, and time using the formula Power=Work/Time;
3. 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)

### Guiding Questions:

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

### Agenda:

• 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

### 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?

Sample problem 2 :

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

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?

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?

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?

### Guided Practice:

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

1. How much work does an elephant do while moving a wagon 40 meters with a pulling force of 400N?
2. If it takes 15 seconds for you to do 3000 J of work, what is your power output?
3. A 900 N mountain climber scales a 200 m cliff. How much work is done by the mountain climber?
4. A small motor does 8000 J of work in 20 seconds. What is the power of the motor in watts?
5. 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?

### 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. 1 flight of stairs/bleachers (5 yards distance between groups)
2. metric ruler
3. stopwatches
4. bathroom scale (lbs)
5. calculator

### Summative Assessment

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

1. What is the work formula equation that you used in class today?
2. What is the power formula equation that you used in class today?
3. John uses 50 N of force to push a shopping cart 10 meters. How much work does he do in joules?
4. 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?
5. How much work is required to pull a sled in order to generate 30 W of power for 5 seconds?
6. 1 newton-meter is equal to 1 _______ of work.
7. Power is usually measured in _______.
8. How much work does a 50 kg person on Earth do if they lift up a barbell 2 meters above the ground?
9. 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?
10. 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?

### 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.