Technological Impacts

1
CLASSWORK

• Complete back of your 3D worksheet.

2
CLASSWORK REVIEW

1. A gardener is capable of applying 50 lbs. to lift
   a wheelbarrow. His hands are placed 4 feet from
   the axle of the wheelbarrow. The weight of the
   compost that he carries is 2 feet from the axle
   of the wheelbarrow. What is the maximum weight
   of compost he can carry?

L DL F DF
?
2 ft.
L x DL F x DF
50 lbs.
L x 2 ft 50 lbs x 4 ft
4 ft.
L x 2 ft 200 ft-lbs
2 ft 2 ft
L 100 lbs.
3
CLASSWORK REVIEW
SO CAN THE CHILD LIFT IT AS DESIGNED?

1. A water pump at the State Park is set up as a
   3rd-class lever. The load that the suction
   inside the pump weighs is 20 lbs. The distance
   from the load to the fulcrum is 18 inches. The
   Park Ranger is wondering if it is possible for a
   child with 15 lbs. of strength to lift the pump
   lever. She is also wondering where an adult who
   can apply a force of 30 lbs. should put their
   hand to lift it. Help her out!

DL 18
L DL F DF
20 lbs.
DF 24
This problem is asking 2 questions. What are
they?
18
15 lbs.
L x DL F x DF
?
20 lbs x 18 15 lbs x DF
360 in-lbs 15 lbs x DF
15 lbs 15 lbs
DF 24
4
CLASSWORK REVIEW

1. A water pump at the State Park is set up as a
   3rd-class lever. The load that the suction
   inside the pump weighs is 20 lbs. The distance
   from the load to the fulcrum is 18 inches. The
   Park Ranger is wondering if it is possible for a
   child with 15 lbs. of strength to lift the pump
   lever. She is also wondering where an adult who
   can apply a force of 30 lbs. should put their
   hand to lift it. Help her out!

DL 18
L DL F DF
20 lbs.
DF 12
18
30 lbs.
L x DL F x DF
?
20 lbs x 18 30 lbs x DF
360 in-lbs 30 lbs x DF
30 lbs 30 lbs
DF 12
5
December 11, 2009
DRILL
Where have you seen an inclined plane used before?
6
TODAYS OBJECTIVES

1. To understand and calculate Mechanical Advantage
   (MA) for various simple mechanisms
2. To review 3D Quiz 2
3. To know and apply the three simple mechanisms
   based on the inclined plane

7
DRILL DECEMBER 14, 2009 CLOSED-NOTES QUIZ
TOMORROW, IF WE ARE QUIET! REVIEW TODAY FOR QUIZ
TOMORROW!

• Get out your Unit 3D Mechanical Technology
  problem sheet.
• Homework-study for the quiz tomorrow. Topics
  covered
• 3 Classes of Levers and examples
• Force and Distance Multipliers
• Engineering Problems

8
FORCE MULTIPLIERS
MECHANICAL ADVANTAGE
MA is the number of times a mechanical device
multiplies the Applied Force
For All Lever Classes
What are the units for MA?
There are no units its a ratio
9
FORCE MULTIPLIERS
You now have 2 equations L x DL F x
DF DF L DL F

Hint Theyre really the same equation rearranged
10
QUIZ REVIEW

• Machines are
• artifacts that transmit or change the application
  of power, force, or motion.
• What is an artifact?
• something created by humans usually for a
  practical purpose.
• Machines can be simple or complex
• Complex machines are comprised of.

Simple Machines
11
QUIZ REVIEW
Principle a law of nature underlying the working
of an artificial device

• Simple machines work on 2 basic principles

LEVER
INCLINED PLANE
12
QUIZ REVIEW

• There are 3 classes of lever

13
QUIZ REVIEW

1. A 1st-class lever is used to lift a bureau that
   weighs 80 lbs. The bureau is located 3 feet from
   the fulcrum. A child who applies the force to
   the other side of the lever has only 20 lbs. of
   strength to push. How far from the fulcrum
   should the child apply the force? (HINT Sketch
   a picture, list the given information, write your
   equation, and solve for the unknown)

3 ft.
DF ?
L 80 lbs.
DL 3 ft.
F 20 lbs.
DF ?
F 20
80 lbs.
14
QUIZ REVIEW
3 ft.
DF ?
L 80 lbs.
DL 3 ft.
DF ?
F 20 lbs.
80 lbs.
F 20
L x DL F x DF
80 lbs x 3 ft 20 lbs x DF
240 ft-lbs 20 lbs x DF
20 ft 20 ft
DF 12 ft
15
QUIZ REVIEW
3 ft.
DF ?
L 80 lbs.
DL 3 ft.
DF ?
DF 12 ft
F 20 lbs.
80 lbs.
F 20
What is the Mechanical Advantage of this lever?
4

16
QUIZ REVIEW
3 ft.
DF ?
L 80 lbs.
DL 3 ft.
DF ?
DF 12 ft
F 20 lbs.
80 lbs.
F 20 lbs.
MA 4 What does F x MA ?
L
17
QUIZ REVIEW

1. A gardener is capable of applying 40 lbs. to lift
   a wheelbarrow. Her hands are placed 3 feet from
   the axle of the wheelbarrow. The weight of the
   compost that she carries is 2 feet from the axle
   of the wheelbarrow. What is the maximum weight
   of compost she can carry?

L DL F DF
?
2 ft.
L x DL F x DF
40 lbs.
L x 2 ft 40 lbs x 3 ft
3 ft.
L x 2 ft 120 ft-lbs
2 ft 2 ft
L 60 lbs.
18
QUIZ REVIEW
3 ft.
DF ?
L 60 lbs.
DL 2 ft.
DF 4 ft.
F 20 lbs.
80 lbs.
F 30 lbs.
What is the Mechanical Advantage of this lever?
2

19
QUIZ REVIEW

1. A water pump at the State Park is set up as a
   3rd-class lever. The load that the suction
   inside the pump weighs is 20 lbs. The distance
   from the load to the fulcrum is 20 inches. The
   park ranger is wondering where an adult who can
   apply a force of 25 lbs. should put her hand to
   lift the pump. The ranger is also wondering
   where another adult who can apply a force of 10
   lbs. should put her hand to lift the pump.

DL 20
L DL F1 DF
20 lbs.
DF 16
This problem is asking 2 questions. What are
they?
20
25 lbs.
L x DL F x DF
?
20 lbs x 20 25 lbs x DF
400 in-lbs 25 lbs x DF
25 lbs 25 lbs
DF 16
20
QUIZ REVIEW

1. A water pump at the State Park is set up as a
   3rd-class lever. The load that the suction
   inside the pump weighs is 20 lbs. The distance
   from the load to the fulcrum is 20 inches. The
   park ranger is wondering where an adult who can
   apply a force of 25 lbs. should put her hand to
   lift the pump. The ranger is also wondering
   where another adult who can apply a force of 10
   lbs. should put her hand to lift the pump.

DL 20
L DL F1 DF
20 lbs.
DF 40
20
10 lbs.
L x DL F x DF
?
20 lbs x 20 10 lbs x DF
400 in-lbs 10 lbs x DF
10 lbs 10 lbs
DF 40
21
CLOSED-NOTES QUIZ TALKING WILL RESULT IN A GRADE
OF ZERO!
22
PRINCIPLE OF THE LEVER
WHEEL AND AXLE
M.A. Radius (D) to Force (F) DF
Radius (D) to Load (L) DL

• Rotary Motion
• the circular motion which occurs when the wheel
  and axle are rotated about the centerline axis.
• Linear Motion
• the straight-line motion which occurs when a
  wheel rolls along a flat surface. The linear
  distance traveled when the wheel completes one
  revolution is equal to the circumference of the
  wheel.
• Circumference Pi Wheel diameter

23
PRINCIPLE OF THE LEVER
PULLEY

• A pulley is an adaptation of a wheel and axle.
  
• A single pulley simply reverses the direction
  of a force.
• When two or more pulleys are connected
  together, they permit a heavy load to be lifted
  with less force.
• The trade-off is that the end of the rope must
  move a greater distance than the load.

24
PRINCIPLE OF THE LEVER
PULLEY
M.A. Total number of strands supporting the load
MA L / F
25
PRINCIPLE OF THE LEVER
PULLEY

• Fixed Pulley when a pulley is attached or fixed
  to a strong member, which will not move.
• How many strands are supporting the load?
• What is the MA of a fixed pulley?
• How many lbs of force are required to lift 100
  lbs of load?
• When a fixed pulley is used, the force needed to
  lift a weight does not change.

1
1
100
26
PRINCIPLE OF THE LEVER
PULLEY

• Movable Pulley splits the work in half.
• How many strands are supporting the load?
• What is the MA of a movable pulley?
• How many lbs of force are required to lift 100
  lbs of load?
• When a movable pulley is used, the force needed
  to lift a load is half that of the load.

2
2
50
27
PRINCIPLE OF THE LEVER
PULLEY

• Block and Tackle a system of three pulleys
• How many strands are supporting the load?
• What is the MA of a movable pulley?
• How many lbs of force are required to lift 120
  lbs of load?
• When a block and tackle is used, the force needed
  to lift a load is 1/3 that of the load.

3
3
40
28
PRINCIPLE OF THE INCLINED PLANE
INCLINED PLANE

• 3 Categories of simple machines based on the
  principle of the INCLINED PLANE

Inclined Plane
Wedge
Screw
29
PRINCIPLE OF THE INCLINED PLANE

• Inclined Plane sloped surfaces used to make a
  job easier
• Easier to go up a slope than a vertical surface
• Wedge used to split, separate, and grip
• Wood chisel, firewood axe, doorstop
• Screw an inclined plane wrapped around a shaft
• 1/2-inch x 12 machine screw
• ½ diameter
• 12 threads per inch

30
PRINCIPLE OF THE INCLINED PLANE

• The inclined plane is the simplest machine of all
  the machines.
• An inclined plane is a flat sloping surface along
  which an object can be pushed or pulled. An
  incline plane is used to move an object upward to
  a higher position.

M.A. Distance D Height H
31
PRINCIPLE OF THE INCLINED PLANE

1. During its use, an inclined plane remains
   stationary, while the wedge moves.
2. With an inclined plane the effort force is
   applied parallel to the slope of the incline.
3. With a wedge the effort force is applied to the
   vertical edge (height) incline.

32
PRINCIPLE OF THE INCLINED PLANE
FORCE
FORCE
D
D
H
H
33
CLASSWORK
Complete the Simple Mechanism Problems worksheet