3 The Six Simple Machines Mechanisms that manipulate magnitude of force and distance.The Six Simple MachinesPulleyLeverWheel and AxleWedgeInclined PlaneScrew
4 Mechanical AdvantageRatio of the magnitude of the resistance and effort forcesRatio of distance traveled by the effort and the resistance forceCalculated ratios allow designers to manipulate speed, distance, force, and function
5 Mechanical Advantage Ratios One is the magic numberIf MA is greater than 1:Proportionally less effort force is required to overcome the resistance forceProportionally greater effort distance is required to overcome the resistance forceIf MA is less than 1:Proportionally greater effort force is required to overcome the resistance forceProportionally less effort distance is required to overcome the resistance forceMA can never be less than or equal to zero.
6 Mechanical Advantage Example A mechanical advantage of 4:1 tells uswhat about a mechanism?Magnitude of Force:Effort force magnitude is 4 times less than the magnitude of the resistance force.Distance Traveled by Forces:Effort force travels 4 times greater distance than the resistance force.
7 *The force needed to overcome friction is not considered* WorkThe force applied on an object times the distance traveled by the objectInitial positionFinal positionForce (F)Distance (d)Work = Force * Distance = F*d*The force needed to overcome friction is not considered*
8 WorkThe product of the effort times the distance traveled will be the same regardless of the system mechanical advantage
9 LeverA rigid bar used to exert a pressure or sustain a weight at one point of its length by the application of a force at a second and turning at a third on a fulcrum.
10 1st Class LeverFulcrum is located between the effort and the resistance forceEffort and resistance forces are applied to the lever arm in the same directionOnly class of lever that can have a MA greater than or less than 1MA =1EffortResistanceResistanceEffortMA <1EffortResistanceMA >1
11 2nd Class Lever Fulcrum is located at one end of the lever Resistance force is located between the fulcrum and the effort forceResistance force and effort force are in opposing directionsAlways has a mechanical advantage >1ResistanceEffort
12 3rd Class Lever Fulcrum is located at one end of the lever Effort force is located between the fulcrum and the resistanceResistance force and effort force are in opposing directionsAlways has a mechanical advantage < 1ResistanceEffort
13 MomentThe turning effect of a force about a point equal to the magnitude of the force times the perpendicular distance from the point to the line of action from the force.M = FdThe terms moment and torque are synonymous.Torque: A force that produces or tends to produce rotation or torsion.
14 Lever Moment Calculation 5.5 in.ResistanceEffort15 lb15 lbsCalculate the effort moment acting on the lever above.M =FdEffort Moment =15 lb x 5.5 in.Effort Moment =82.5 in. lb
15 Lever Moment Calculation When the effort and resistance moments are equal, the lever is in static equilibrium.Static equilibrium:A condition where there are no net external forces acting upon a particle or rigid body and the body remains at rest or continues at a constant velocity.
16 Lever Moment Calculation EffortResistance5.5 in.?36 2/3 lb15 lb15 lbsUsing what you know regarding static equilibrium, calculate the unknown distance from the fulcrum to the resistance force.Static equilibrium:Effort Moment = Resistance Moment82.5 in.-lb = 36 2/3 lb x DR82.5 in.-lb /36.66 lb = DRDR = 2.25 in.
17 Lever IMA Resistance Effort Both effort and resistance forces will travel in a circle if unopposed.Circumference is the distance around the perimeter of a circle.Circumference = 2 p rDE = 2 π (effort arm length)DR = 2 π (resistance arm length)______________________2 π (effort arm length)IMA =2 π (resistance arm length)
18 Levers in the Body Class 1: Triceps Extension Class 2: Heel Lift Class 3: Biceps Curl
19 Wheel & Axle Can you think of an example of a wheel driving an axle? A wheel is a lever arm that is fixed to a shaft, which is called an axle.The wheel and axle move together as a simple lever to lift or to move an item by rolling.It is important to know within the wheel and axle system which is applying the effort and resistance force – the wheel or the axle.Can you think of an example of a wheel driving an axle?
20 Wheel & Axle IMAǾ6 in.Ǿ20 in.Both effort and resistance forces will travel in a circle if unopposed.Circumference = 2pr or πdDE = π [Diameter of effort (wheel or axle)]DR = π [Diameter resistance (wheel or axle)]______________________IMA =π (effort diameter)π (resistance diameter)What is the IMA of the wheel above if the axle is driving the wheel?6 in. / 20 in. = .3 = .3:1 = 3:10What is the IMA of the wheel above if the wheel is driving the axle?20 in. / 6 in. = 3.33 = 3.33:1
21 PulleyA pulley is a lever consisting of a wheel with a groove in its rim which is used to change the direction and magnitude of a force exerted by a rope or cable.
22 Pulley IMA Movable Pulley - 2nd class lever with an IMA of 2 Fixed Pulley- 1st class lever with an IMA of 1- Changes the direction of force10 lb5 lb5 lbMovable Pulley- 2nd class lever with an IMA of 2- Force directions stay constant10 lb10 lb
23 Pulleys In Combination Fixed and movable pulleys in combination provide mechanical advantage and a change of direction for effort force.80 lbWhat is the IMA of the pulley system on the right?10 lb4Movable pulleys in combination provide mechanical advantage without change in effort force direction.20 lb40 lbWhat is the IMA of the pulley system on the left?8Pulley IMA = Total number of strandssupporting the load800 lb
25 Mechanical Advantage Example A mechanical advantage of 4:1 tells uswhat about a mechanism?Magnitude of Force:Effort force magnitude is 4 times less than the magnitude of the resistance force.Distance Traveled by Forces:Effort force travels 4 times greater distance than the resistance force.
26 Inclined PlaneA flat surface set at an angle or incline with no moving partsAble to lift objects by pushing or pulling the load
27 Inclined Plane IMA DE = Distance traveled by the effort = L 15.0 ft4.0 ftDE = Distance traveled by the effort = LDR = Distance traveled by the resistance = HWhat is the IMA of the inclined plane above?IMA = 15.0 ft / 4.0 ft = 3.75 = 3.8:1
28 Wedge Functions as a moving inclined plane Tapers to a thin edge and is used for splitting, raising heavy bodies, or for tightening by being driven into something
30 Wedge IMA DE = Distance traveled by the effort = L T ftL ftDE = Distance traveled by the effort = LDR = Distance traveled by the resistance = TWhat is the IMA of the wedge on the right?IMA = 10.0 ft / 3.0 ft = 3.33 = 3.3:1
32 ScrewTwo ComponentsAn inclined plane wrapped around a cylinder, forming the path and pitchA wheel and axle used to create rotary motionPropertiesChange rotary motion into linear motionUsed as a threaded fastenerLarge MALarge amount of friction loss
33 Screw Identification Thread Information DiameterEffort Arm Distance – If using a wrench, effort arm distance would be the length of the wrenchThread Information1/2 13 NCDiameterThreads per inchThread description coarse or finePitchDistance between threads and linear distance traveled by 1 rotation of the screwIf 13 threads per inch, then pitch or distance between threads is 1/13 of an inch.How far will a screw with 13 threads per inch move linearly if turned one full rotation?1/13 of a inch
34 Screw IMA1/4 20 NCDE = One rotation of the effort arm = CircumferenceDR = Linear distance traveled during one rotation of the effort arm = PitchWhat is the IMA of the screw above if effort is applied by an 8.0in. long wrench?