1. No – you are NOT getting paid for this!
Work, Power &
Simple Machines
No – you are NOT getting paid for this!

3. Video Work and Power TAKE NOTES

4. What is Work? Work means several different things in everyday life…
You work on science problems.
Your parents go to work.
Your toaster doesn’t work.
Taking out the trash is too much work.
Work means only one thing in physics…
Work is force times distance.
To be exact – WORK is force times the distance moved in the direction of the force.

5. Calculating Work W = F x d
The formula to calculate work is…
W = F x d
Units for Work are – Joules (J) or Newton-meters (Nm)
Units for Force are – Newtons
Units for Distance are - meters

6. Calculating Work - Continued
Like some of the other formulas we have worked on during class – the work formula can be manipulated by using a triangle.
So, to find FORCE, we need to DIVIDE work and distance.
Divide
Multiply W
F = W d
Joules or Newton Meters
And, to find DISTANCE, we need to DIVIDE work by force. F d
Newtons
Meters
d = W F

7. Calculating Work - Continued
A box weighing 2.0 N is lifted 4m. How much work was done?
Step 1 Read the problem. Draw a picture.
Step 3 Set up the formula.
Step 4 Substitute the numbers. Solve. Box Answer
with units.
Step 2 Write down what you know. What are you trying to find?
8Joules
Formula
Substitute
Answer
W =
2.0 N
F =
W = FXd
W = 2.0 NX4m
W = 8 Joules
D = 4m

8. Do problems 1 & 2 on your notes.

9. What is Power? Power is … The rate at which WORK is done.
a measure of the amount of WORK done in a certain amount of time.

10. Calculating Power P = W T P = F x d T Units for Power are – Watts
The formula to calculate power is…
P = W T
P = F x d T
Units for Power are – Watts
Units for Work are – Joules
Units for Time are - Seconds
1 Watt is = 1 Joule/sec

11. Calculating Power - Continued
Use the triangle to manipulate the Power formula.
So, to find WORK, we need to MULTIPLY power and time. W
Divide
Joules or Newton Meters
W = P X T
And, to find TIME, we need to DIVIDE work by power. P T
Watts
Seconds
Multiply
T = W P

12. Calculating Power - Continued
A figure skater lifts his partner, who weighs 450 N, 1.0 m in 3 seconds. How much power is required to lift his partner?
Step 1 Read the problem. Draw a picture.
Step 3 Set up the formula.
Step 4 Substitute the numbers. Solve. Box Answer
with units.
Step 2 Write down what you know. What are you trying to find?
Formula
Substitute
Answer
150 Watts
P =
P = 450N X 1.0m
3 sec
P = W T
W =
450N X 1.0m
P =150 Watts
3 sec
T =

13. Do problems 3 & 4 on your notes.

14. What is a Simple Machine?
Is a device that does work with only one movement.
Helps us do WORK by reducing our EFFORT – not the amount of work done.

15. Types of Simple Machines
LEVER –
Board that rests on a turning or pivot point.
Turning / Pivot point is called the FULCRUM
The object the lever moves is the LOAD or the
RESISTANCE.
The EFFORT is the force used to move the
object.
The closer the resistance is to the
FULCRUM, the easier it is to move.

16. Effort – what’s moving it
Classes of Levers –
First Class Levers
Fulcrum is between the Resistance & Effort
Resistance – what’s
being cut
Fulcrum – pivot point
Effort – what’s moving it

17. Effort – what’s moving it
Classes of Levers –
Second Class Levers
Resistance is between the Fulcrum & Effort
Resistance – what’s
inside
Effort – what’s moving it
Fulcrum – pivot point

18. Effort – what’s moving it
Classes of Levers –
Third Class Levers
Effort is between the Fulcrum & Resistance
Fulcrum – pivot point
Effort – what’s moving it
Resistance – what’s
being pushed

19. If it were FRE you would remember!
How Do I Remember the Classes of Levers?
What is located in the middle determines the class of level. F
First Class
Lever R
Second Class
Lever E
Third Class
Lever
If it were FRE you would remember!

20. Types of Simple Machines - Continued
2. INCLINED PLANE –
Flat surface that is higher on one end
Used to make things move from a higher to
lower place or lower to higher place
Examples: Ramps, Slides, Path up Hill,
Ladders

21. Types of Simple Machines - Continued
3. WHEEL & AXLE –
Rod that goes through wheel that lets the wheel turn.
Used to help make things turn in circular motion
Examples: Cars, Roller Skates, Door Knobs,
Fans and Faucets
Gears-toothed wheel and axle

22. Types of Simple Machines - Continued
4. SCREW –
Inclined plane wrapped about a cylindrical post.
Used to raise and lower things or hold objects
together
Has ridges – not smooth like a nail
Examples: Jar lids, Light bulbs, and
Spiral Stairs

23. Types of Simple Machines - Continued
5. WEDGE –
Two inclined planes pushed that meet to form a sharp edge.
Used to split two things apart.
Examples: Fork, Knife, Door Stop and Ax

24. Types of Simple Machines - Continued
6. PULLEY –
Made of a wheel with a groove and a rope or chain that fits into the groove.
One part of the pulley (usually the rope) is
attached to the Load (Resistance)
When you pull on the other side of the rope,
the wheel turns and the load moves.
Examples: Flag Poles, Sailboats, Blinds &
Cranes

25. Block & Tackle – A system of ropes and pulleys that multiplies forces.
Often seen in garages to lift engines out of cars.

26. What is a Compound Machine?
Is a combination of two or more simple machines.
Examples – Bikes, Forklifts, Pencil Sharpener