1. ENERGY

2. Energy
Energy- the ability to do work
SI unit: Joules

3. Mechanical Energy
Mechanical Energy- Energy do to the position or movement of an object
For example, a rollercoaster has mechanical energy in the form of both potential and kinetic energy. Explain.

4. Potential Energy Stored Energy / energy of position
amount depends on position or condition of the object

5. Gravitational Potential Energy
Gravitational Potential energy is greater when the object’s height is greater
G. PE is greater when the object’s weight is greater

6. Which has more PE, a plant sitting on a 5th floor window or one sitting on a 1st floor window? Why?

7. PE formula
PE= mass x 9.8 x height
Units
Mass= grams
Height=meters

8. Example PE Problem Mass= 65 kg Height= 35 m Gravity accel= 9.8 PE= ?
PE= 65 x 9.8 x 35
= Joules

9. PE word problem
Calc. PE
1200 kg car at the top of a hill that is 42 m high
M= 1200
9.8
h= 42
1200 x 9.8 x 42 = Joules

10. Kinetic Energy “Energy in Motion”
Will change more due to velocity (bc its squared) than mass

11. Kinetic energy KE is greater when the speed is greater.
KE is greater when the mass of the object is greater.
Which is more kinetic energy a motorcycle going 35mph or an 18 wheeler going 35 mph? Why?

12. Kinetic Energy Formula
KE= ½ mass x velocity2

13. Kinetic Energy Ex Problem
Mass= 44 kg
Speed= 31 m/s
KE= ?
KE= ½ mass x velocity2
22 x 961= Joules

14. KE Word Problem
Calc KE of 1500 kg car that is moving at a speed of 700m/s
KE= ½ mass x velocity2
750 x = Joules

15. From PE to KE

16. Conservation of Energy
“Energy cannot be created or destroyed”
changes forms
The total amount of energy NEVER changes

17. More Forms of Energy
Chemical Energy- has to do with ions, atoms, molecules, and bonds
Change to another form of energy when a chemical reaction occurs
Food, Wood, Gasoline, Heating oil
Electrical Energy- associated with voltage and current

18. More Forms of Energy
Thermal Energy- associated with the movement of molecules
More Motion = More Heat

19. Sound Energy- associated with longitudinal mechanical waves

20. Light Energy- associates with electromagnetic waves
Light, X-rays, Lasers, Gamma Rays

21. Nuclear Energy Energy associated with Fission and Fusion Sun and Stars
Occurs only in controlled situations on earth

22. Energy Transformations
According the Law of Conservation of Energy…
Energy can change forms
Energy in battery then a light turns on
Potential or chemical to electrical

23. More Energy Transformations
Plant sitting in the sun, then making food then growing
Light energy to chemical energy to kinetic energy
Making music playing the piano
Potential to kinetic to sound

24. Energy Conversions

25. Which of the seven main forms of energy is present in each situation?

26. Work Work= the force exerted over a distance
When work is done, energy is transferred to the object
If no movement, Zero work!

27. When force is applied to an object and it moves, work is done, and kinetic energy is created
The greater the force, the greater the kinetic energy of the object

28. If work is done and an object is lifted, the object gains PE
The higher it is lifted, the more PE

29. Work Triangle Calculating Work: Work= Force x Distance
SI Unit: Joules (J) = 1 Newton*Meter W D F

30. Example Work Problem F= 30 N d= 1.5m W= ? W= F *d 30 * 1.5 = 45
W= 45 J W D F

31. Example Work Problem
A carpenter lifts a 45 N beam 1.2 m high. How much work is done on the beam?
F= 45 N
D= 1.2 m
W= ?
W= F * D
45 * 1.2 = 54
W= 54 J W D F

32. Multiple Step
A dancer lifts a 45 kg ballerina overhead a distance of 1.4 m. How much work is done?
F= ?
D= 1.4m
W= ?
W= F * d
441 * 1.4 = J
W= J
45 * 9.8= 441 N W D F

33. Last one
The same dancer holds the ballerina overhead for 5 seconds. How much work is being done?
None, no distance is being traveled.

34. Power The rate at which work is done
SI unit: Watts (w) = 1 Joule per second
Formula= Power = Work / Time W P T

35. Example Problem: W= 500 J T= 20 s P= ? P T P= W / T 500 / 20 = 25
P= 25 watts W P T

36. Example Problem # 2 F= 450 N d= 1.0 m t= 3 s W= ? P = ? P T W= F * d
450 * 1 = 450
W= 450 J
P = W / t
450 / 3 = 150 watts
P = 150 watts W P T

37. Word Problem
A mover carries a chair up the stairs in 30 seconds. His work totals 300 Joules. What was his power?
P = w / t
300 / 30 = 10
P= 10 watts W P T

38. Last one
Mary runs up the stairs in 22 seconds. Carrie runs up the stairs in 27 seconds. Each girl has a work total of 240 Joules. Which has more power?
Carrie
W= 240
T= 27
240 / 27 = 8.89
P= 8.89 watts
Mary
W= 240
T= 22
240 / 22= 10.91
P= Watts

39. Machines change the force that you exert in either size or direction.
Simple Machine- one movement
Compound Machine- more than one movement

40. Machines at work 2 forces involved with machines
Input Force (In) – force applied to the machine
Output Force (Out)- force applied by the machine to overcome resistance

41. Machines at Work
Mechanical Advantage- # of times the machine multiplies input force
MA= input force / output force
MA= input / output
Out MA In

42. Example Problem Output = 500 N Input = 20 N MA= ? MA= Output / Input
500 / 20 = 25
MA= 25
Out MA In

43. Another example Output = 2000 N Input= ? MA= 10 MA= Output/ Input
Input= Output / MA
2000 / 10 = 200 N
Input= 200 N
Out MA In

44. Word Problem
The power steering in an car has a mechanical advantage of 75. If the input force to turn the steering wheel is 49 N, what is the output force of the car’s front wheels?
Output= 3675 N
MA= 75
Input= 49 N
Output= ?
Output= MA * Input
75 * 49 = 3675 N
Out MA In

45. 2 families of Simple Machines
Levers
Inclined planes

46. Simple Machines Lever- arm that turns around a fixed point
FULCRUM- fixed part

47. Types of Levers
1st Class
2nd Class
3rd Class
classified on location Input force, Output force, and fulcrum

48. First Class Lever Fulcrum between Input force and Output force
Can multiple force or distance
Ex: Scissors, pliers, clothes pin

49. 2nd Class Lever Output between Input force and fulcrum Multiply force
Examples: Wheel Barrel

50. 3rd Class lever Input force between Output force and fulcrum
Increase distance
Examples: bicep, fishing rod, hockey stick

51. Pulleys Modified Lever
grooved wheel with a rope or chain running along the groove
Single, fixed pulley has an MA of 1

52. Pulley Moving Pulley- has an MA of 2
Block and Tackle Pulley- multiple pulleys put together. Increases MA

53. Wheel and Axle Lever family
2 wheels of different sizes that rotate together
Smaller wheel is called the axle

54. Inclined Plane
Inclined Plane- a sloping surface used to raise objects (such as a ramp)
you exert less input force over a greater distance

55. Screw and Wedge
Screw- inclined plane wrapped in a spiral around a cylindrical post
Ex:
Wedge- inclined plane with one or two sloping slides
Ex: Chisel, knives, ax blade

56. COMPOUND MACHINES
Compound Machine- a combination of two or more simple machines
Examples: Bicycle (2 wheel and axle), the axle (wedge and lever)

57. Efficiency in Machines
With machines, not all work is useful
Some lost as heat, through friction,
Efficiency- measure of how much useful work a machine can do
Efficiency= useful work output
work input

58. Efficiency Problem Work input= 180 J Useful work output= 140 J