1. Introduction to Work, Power & Kinetic Energy
P H Y S I C S
   
Introduction to Work, Power & Kinetic Energy

2. What is Work?
What do you think of when you think of work?

3. Work
Work is done when a force acts parallel to the direction of the displacement
Force
Displacement
Force
Displacement

4. Work
Work is done when a force acts parallel to the direction of the displacement
Friction Force
Displacement
Air
Resistance Force
Displacement

5. Work or Not?
Man holds out heavy concrete block at arm’s length for 10 minutes
Student pushes car down street
Women holds up a large box over-head while walking down the hall way
Child pushes a cart along the side walk
NOT WORK
WORK
NOT WORK
WORK

6. What is kinetic energy?
What do you think of when you think of kinetic energy?

7. Kinetic Energy Any moving object has kinetic energy Amount depends on
1) velocity
2) mass

8. Kinetic Energy Equation
𝐾𝐸= 1 2 ∙𝑚∙ 𝑣 2 KE  kinetic energy (J) m  mass (kg) v  velocity (m/s) Note: ∆𝐾𝐸=𝐾𝐸 − 𝐾𝐸 𝑜

9. Kinetic Energy

10. Work-Energy Theorem
Work done on an object is equal to its change in kinetic energy
W = ∆KE
W  work (J)
∆KE  change in kinetic energy (J)
Note: ∆𝐾𝐸=𝐾𝐸 − 𝐾𝐸 𝑜

11. Work-Energy Theorem
+W increases KE
WORK

12. Formula for Work W = f * d W  Work (J) f  Force (N)
d  Displacement (m)

13. What is power?
What makes something powerful?

14. Power
The rate at which work is done

15. Work vs. Power
Power accounts for “how fast” work is done A B

16. Power Equation P= 𝑊 𝑡 Unit: 𝐽 𝑠 =𝑊 (𝑊𝑎𝑡𝑡𝑠) P  power (W) W  work (J)
t  time (s)

17. Power Equation Another variation derived from v= 𝑑 𝑡 : P=𝐹·𝑣
P  power (W)
F  force (N)
v  velocity (m/s)

18. Household Appliances 60W light bulb - 60W Toaster : 800-1500W
Microwave : W
Dishwasher : W
Washing Machine : 500W
Vacuum Cleaner : W
Clothes dryer : 4000W
Ceiling Fan : 10-50W
Hair Blow dryer : 1000W
Laptop Computer : 20-50W
Desktop Computer : W
Cell Phone Charger: 3-5W
iPod/iPad Charger: 10W

19. Time to explore Power What do we need to know to calculate power?
What is your force?
So if 1lb=2.2kg how much mass do you have?
How can we calculate velocity?

20. On a sheet of paper Calculate your Fg.
Now let’s go to the stairs and see who can generate the most power.
When we get back calculate your power. This paper is your exit slip. You can’t leave until it’s done.