1. Work, Power, and Simple Machines
Chapter 14
Work, Power, and Simple Machines

2. Force acting through a distance
Work
Must be movement
Work = force x distance
Joule
meters
Newton

3. If the direction of the movement is Not the same as the force… NO work is done!
applied force
Motion 
Motion 
Applied force 

4. Is Work Done?

5. SI unit of Work
Joule = Newton x meter
(J) = N x m

6. A weight lifter lifts a 1600 newton barbell over his head
A weight lifter lifts a 1600 newton barbell over his head. The barbell is lifted to a height of 2.0 meters. Calculate the work done. Work = Force x Distance

7. A student rows a boat across a still pond with a force of 72 newtons
A student rows a boat across a still pond with a force of 72 newtons. The student travels a distance of 13 meters Calculate the work done. Work = Force x Distance

8. Involves time
Power
How fast is work done?
Power = Work / time
Watts
Joules
seconds
Large amounts of power are measured in kilowatts

9. Doing work faster requires more power.
You can increase the amount of work done in a given time. OR
You can do a given amount of work in less time.

10. SI unit of Power
Watt = Joule  second
(W) = J/s

11. A truck pulls a trailer at a constant velocity for 100 m while exerting a force of 480 N for 1 minute (60 s). Calculate the work done and the power. Work = Force x Distance Power = Work  time

12. Complete the Math Practice on page 415

13. Horse-power
equal to 750 watts
1 strong horse can move a 750 N object 1 meter in 1 second
1 hp = small electric motor
family car = 100 hp
diesel train = 10,000 hp

14. Energy, Work, Power, and Energy Worksheet Answers

15. Part 1: Work and Power
1. Amy uses 20-N of force to push a lawn mower 10meters. How much work does she do?

16. Part 1: Work and Power
2. Frank does 2400-J of work in climbing a set of stairs. If he does the work in 6 seconds, what is his power output?

17. Part 1: Work and Power
3. A girl weighing 420 Newtons takes 55 seconds to climb a flight of stairs 18 meters high. What is her power output vertically?

18. Part 1: Work and Power
4. How much work does an elephant do while moving a circus wagon 20 meters with a pulling force of 200-N?

19. Part 1: Work and Power
5. A 40 N force is used to push a 2.00 kg cart a distance of 5 meters. What is the work done on the cart?

20. Part 1: Work and Power
6. A 900-N mountain climber scales a 100 meter cliff. How much work is done by the mountain climber?

21. Part 1: Work and Power
7. A small motor does applies a 200N force over 10m in 20 seconds. What is the power of the motor in watts?

22. Section 14:2
WORK AND MACHINES
Yes…machines do work

23. makes work easier increase force increase distance
Machine
increase force
increase distance
change the direction
Work Input
Work applied to the machine by you
Work Output
Work done by the machine

24. Work Input =
Input Force x Input Distance
Work Output =
Output Force x Output Distance

25. 14:3 Mechanical Advantage
Number of times a machine multiplies the force applied
Ex. Cracking Pecans

26. Actual Mechanical Advantage
The mechanical advantage determined by measuring the actual forces acting on a machine.
Actual Mechanical Advantage =
Output Force
Input Force

28. Ideal Mechanical Advantage
The mechanical advantage in the absence of friction.
Ideal Mechanical Advantage =
Input Distance
Output Distance

30. A woman drives her car onto wheel ramps to perform some repairs
A woman drives her car onto wheel ramps to perform some repairs. If she drives a distance of 1.8 meters along the ramp to raise the car 0.3 meter, what is the ideal mechanical advantage (IMA) of the wheel ramps?
IMA = Input Distance
Output Distance

31. Complete the Math Practice on Page 425.6 10 m

32. Part 2: Machines and Mechanical Advantage1.

33. 2.

34. 3.

35. Part 3: Torque
The drawing above represents a wrench. The left end of the wrench is attached to a bolt. Four equal forces of 100N are applied as indicated in the drawing.
A. A 100N force would cause the most torque if it was placed at which letter above? (Why)
B. What is the torque at A
C. What is the torque at C

36. 4. What is the boy weight in order for the see-saw to be in equilibrium?

37. 5. How far is the boy from the fulcrum in the see-saw in equilibrium below?

38. How much work input is used to create work output
Efficiency
Eff. = Work output x 100%
Work input
Ex. Gas mileage = Miles driven
Gallons of gas

39. Complete the Math Practice on Page 426.

40. 14:4Simple Machines Does work with one movement Six Types:
√ Lever √ Wheel & Axle
√ Inclined Plane √ Wedge
√ Screw √ Pulley

41. Lever
bar that is free to pivot around a fixed point called a ________.
fulcrum
Classified in 3 categories

42. fulcrum
1st class: The _______ is located between the ______ and the _________.
effort
resistance
Output Force
Input Force
Fulcrum
Ex. Seesaw, crowbar

43. 2nd class: The ________ is located between the ______ and the _______.
resistance
fulcrum
effort
Output Force
Input Force
Fulcrum
Ex. Wheelbarrow, hole punch

44. effort
3rd class: The ________ is located between the ______ and the __________.
fulcrum
resistance
Output Force
fulcrum
Input Force
Ex. Baseball bat, rake

46. Wheel and Axle _______ sized wheels rotating together.
Different
Ex: door knob, tires, can opener

47. Inclined Plane Sloping surfa ce Ex: ramp, slide IMA = length/height 12
Sloping surfa ce
Ex: ramp, slide
IMA = length/height 12 5 4 4

48. Wedge
An inclined plane that moves
Ex. Axe, sledgehammer

49. Screw An inclined plane wrapped around a cylinder
An inclined plane wrapped around a cylinder
Ex. Light bulb, bolts, lids

50. Let’s make our own screw
Take out a sheet of paper.
Fold it at an angle.
Tear along the crease.
Slowly wrap it around your pen or pencil.
Turn your pen/pencil.

51. PULLEYS _______ with a rope, chain, or cable. Three different types
Cylinder
_______ with a rope, chain, or cable.
Three different types

52. A wheel is attached in a fixed location.
Fixed Pulley
A wheel is attached in a fixed location.
Rotate in place.
Ex. flagpole

53. Attached to the moving object.
Movable Pulley
Attached to the moving object.
Ex. Sails

54. Pulley System
Combines fixed and movable pulleys
Ex. Crane

56. Bill Nye simple machines

57. Compound Machines
Combination of two or more simple machines that operate together.
Ex. Car, watch, washing machine