January 4, 2010 Quietly get out Problem Set 2 Solutions (classwork/ homework) for a review today. U3d-L9 DRILL

U3d-L1 F x d = W Wo / Wi = Eff

U3d-L1 The technology of putting together mechanical parts to produce, control, and transmit motion. Example applications: Gear systems in a car transmission, Brakes on a bicycle, Agitator in a washing machine, Latch on a door. Springs in vehicle shocks

U3d-L1 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…. Inputs go in Outputs come out Simple Machines

U3d-L1 1. COMPONENTS: –Levers –Pivot Points –Linkage Joints INPUT

U3d-L1 INSTRUCTIONS: Transmit the given input motion to the desired output motion using only the allowed components. input Correctly copy the following onto the remaining 2” x 2” boxes in your notebook.

1. A hot air balloon carries 200 lbs cargo, 150 lbs human, and 200 lbs materials up a distance of 2,000 feet. How much work did the balloon do (keep all units)? U3d-L3 2.A physical therapy doctor told his 150-lb patient to do 30,000 ft-lbs of work each day to rehabilitate his leg. The patient decides to climb a hill to perform this work. How high does the patient need to climb in order to meet his goal? 1. F x d = W 550 lbs x 2,000 ft = W = 1,100,000 ft-lbs. 2. F x d = W 150 lbs x d = 30,000 ft-lbs. 150 lbs. d = 200 ft.

1. You have a dog that weighs 50 pounds. You carry her up the stairs a total vertical height of 9 feet. How much work did you do (keep all units)? U3d-L Hummer H2 Output = 320 miles Input = 32 gallons Efficiency = ? Toyota Prius Output = 500 miles Input = 10 gallons Efficiency = ? F x d = W 50 lbs x 9 ft = W = 450 ft-lbs.

U3d-L2 DRILL (continued) Hummer H2 Output = 320 miles Input = 32 gallons Efficiency = ? Toyota Prius Output = 500 miles Input = 10 gallons Efficiency = ? Wo / Wi = Eff 320 mls / 32 gal = Eff = 10 mpg Wo / Wi = Eff 500 mls / 10 gal = Eff = 50 mpg

Identify which Core technology is represented by the examples below: U3d-L4 a.Door latche. Crankshaft b.Thermostatf. Cylinder c.Fang. Battery d.Light bulbh. Gas tank a.Mechanical b.Electronic c.Mechanical/Thermal d.Optical e.Mechanical f.Structural g.Electrical h.Structural

U3d-L4 3 Categories of simple machines based on the principle of the LEVER: LEVER LeverWheel and AxlePulley

Lever Arm Fulcrum Applied Force Load 3 different Classes of levers: U3d-L4 LEVER

Which is 1 st class? U3d-L4 1 st class: –The fulcrum is between the load and the effort force LEVER

Which is 2 nd class? U3d-L4 2 nd class: –The load is between the effort and the fulcrum LEVER

Which is 3 rd class? U3d-L2 3 rd class: –The effort is placed between the load and the fulcrum LEVER

U3d-L4 Notice the direction of motion of the Force and Load for each of the 3 classes of lever.

Sketch the pictures below and answer the questions: Which lever would be easier to push down, A or B? Which load will travel the greater distance, A or B? U3d-L5 AB Demonstrate it

U3d-L5 Simple machines work on 2 basic principles: LEVER INCLINED PLANE Principle: a law of nature underlying the working of an artificial device

U3d-L5 Which class is the lever below? Describe it. FIRST CLASS SECOND CLASS THIRD CLASS

U3d-L5 A shaft attached to a disk WHEEL-and-AXLE

U3d-L5 Which class of lever? WHEEL-and-AXLE 2 nd Class

U3d-L5 Which class of lever? WHEEL-and-AXLE 3 rd Class

U3d-L5 Pulleys are grooved wheels attached to an axle. Generally, what class lever do they act as? PULLEYS 1 st Class

U3d-L5 Simple Machines can be: –Force Multiplier: Increases the force applied to the work at hand –Distance Multiplier: Increases the distance the load moves FORCE/DISTANCE MULTIPLIERS

U3d-L5 From the drill: –Which is the force multiplier? In other words, which arrangement gives you greater strength FORCE/DISTANCE MULTIPLIERS AB

U3d-L5 From the drill: –Which is the distance multiplier? In other words, which arrangement gives you greater distance FORCE/DISTANCE MULTIPLIERS AB

MECHANICAL ADVANTAGE FORCE MULTIPLIERS F L DLDF For All Lever Classes What are the units for MA?There are no units – it’s a ratio DF DL M.A.= LFLF = MA is the number of times a mechanical device multiplies the Applied Force U3d-L8

You now have 2 equations: L x DL = F x DF DFL DLF FORCE MULTIPLIERS = Hint: They’re really the same equation rearranged

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 U3d-L8

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 U3d-L8 WHEEL AND AXLE

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. U3d-L8 PULLEY

U3d-L8 M.A. = Total number of strands supporting the load MA = L / F 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. U3d-L 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. U3d-L 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. U3d-L PULLEY

3 Categories of simple machines based on the principle of the INCLINED PLANE: INCLINED PLANE Inclined PlaneWedgeScrew U3d-L8

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 U3d-L8

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. H D L F M.A.= Distance = D Height H

U3d-L8 FORCE 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.

U3d-L8 DHDH M.A.= FORCE D D H H