# Simple Machines Notes

• Simple machines
• Mechanisms that manipulate magnitude of force and distance
• Input, process, and output
• Engineers like to manipulate things to make things easier
• The six Simple machines
• lever
• it allows you to do use leverage to increase work done using a fulcrum which is necessary for operation
• Examples
• Bottle opener
• Seesaw
• Scissors
• Door
• Door handle
• wheel and axle
• simplest wheel and axle example would be a bicycle
• pulley
• most important
• Examples
• crane
• elevator (multiple)
• things on the boat that lifts up the net
• fishing rod
• inclined plane
• flat surface
• two dimensions and it is infinite (mathematically) - plane
• in order to locate something in a plane, you have two values
• the purpose is that is decreases work in order to make something to make something higher
• this then increases potential energy
• In the US, olympic athletes like to practice in Denver so they can get used to the lack of oxygen
• wedge
• two inclined planes connected at the end (rough definition)
• Examples
• nail
• knife
• axe
• hatchet
• crowbar - also a lever
• door stopper
• screw
• contains one long inclined plane
• Goal is use less force and do more work
• Examples of this:
• Moving things
• Sending messages
• Lifting something with a pulley
• Hammer
• Multiple pulleys which allows for a multiplication of effort
• You can also manipulate the distance.
• Force times distance is work
• Coupon means a small piece of a bigger piece, example is when you take a sample of a larger thing for testing purposes
• Ratio of the magnitude of the resistance and effort forces
• Ratio of distance traveled by the effort and the resistance force
• Resistance force is the force that is working against what you are trying to do (the force that is resisting your work
• If you have a car that you are driving, resistance forces are:
• wind
• the texture of the road (gravel, concrete, etc.)
• etc.
• Effort force is the amount of the work that you are trying to do and you are attempting to overcome the resistance
• Example
• A mechanical advantage of 4:1 tells us what about a mechanism?
• It tells us that the ratio of the effective work vs the amount of work that was actually put in. In other words, it is how easy it is. The higher the first number is, the easier it is to do whatever it is you are doing.
• The effort force magnitude is 4 times less than the magnitude of the resistance force
• Effort force travels 4 times greater distance than the resistance force
• Mechanical advantage equals the resistance force (Fr) divided by the effort force (Fe)
• Calculated ratios allow designers to manipulate speed, distance, force, and function
• Work
• The force applied on an object times the distance traveled by the object
• Work = Force * Distance = F*d
• Note: The force needed to overcome friction is not considered (this is an example of a qualifying statement)
• Another note: anything engineerings do is based on some type of assumption
• Magical Advantage Ratios
• One is the magic number
• If MA is the greater than 1:
• Proportionally less effort force is required to overcome the resistance force.
• Proportionally greater effort distance is required to overcome the resistance force
• Mechanical advantage can never be less than or equal to 0
• Ideal Mechanical Advantage (IMA)
• Theory-based calculation
• Friction loss is not taken into consideration
• Ratio of distance traveled by effort and resistance force
• Used in efficiency and safety factor design calculations
• IMA = De/Dr where De = Distance traveled by effort force and Dr = Distance traveled by resistance force
• Actual Mechanical Advantage (AMA)
• Inquiry-based calculations
• Frictional losses are taken into consideration
• Used in efficiency calculations
• Ratio of force magnitudes
• AMA = Fr/Fe where Fr = Magnitude of the resistance force and Fe is the magnitude of the effort force.
• Real World Mechanical Advantage
• Can you think of a machine that has a mechanical advantage less than one?
• Go to gym and the machines there are designed to make your life harder so they have a mechanical advantage that is less than one
• Course for military training
• Lever
• A rigid bar (a solid that has a longer length than width or depth) 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.
• 1st Class Lever
• Fulcrum is located between the effort and the resistance force.
• Effort and resistance forces are applied to the lever arm in the same direction
• Only class of lever that could have a MA greater than or less than 1
• Gantry/girder is like an upside down seesaw
• You can change mechanical advantage by changing forces or moving the fulcrum
• 2nd Class Lever
• Fulcrum is located at one end of the lever
• Resistance force is located between the fulcrum and the effort force.
• Resistance force and effort force are in opposing directions.
• Always has a mechanical advantage >1
• The resistance is always in between what you are trying to do and the fulcrum
• 3rd Class Lever
• Fulcrum is located at one end of the lever
• Effort force is located between the fulcrum and the resistance
• Resistance force and effort force are in opposing directions
• Always has a mechanical advantage <1
• Rotating something is called moment - Google this more
• Force times the distance is the moment
• Moment
• The 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.
• Cantilever is a lever that is only supported at one and and the other end is free
• Deformation is when something deforms, changes shape
• CMU is a cinderblock wall
• When you have a canopy, you need a solid concrete bond beam attached to it inside of the house to hold the canopy up.
• On the lever moment calculation slide, it is 82.5 at the fulcrum. It is attempting to move counterclockwise as well
• Moment = Force X Distance
• Effort Moment = 15 lb x 5.5 in
• Effort Moment = 82.5 in. lb
• When the effort and resistance moments are equal, the lever is in static equilibrium
• Fulcrum helps to change the rotational direction
• Static Equilibrium is where there are no net external forces acting upon a particle or rigid body and the body remains at rest of continues a constant velocity
• The difference between a particle and a rigid body is that a particle can be anything while a rigid body must be rigid (fixed shape)
• Static equilibrium occurs when effort moment is equal to the resistance moment
• Lever IMA
• Both effort and resistance forces will travel in a circle if unopposed
• Circumference is the distance around the perimeter of a circle
• Circumference = 2(pi)r
• De = 2(pi)effort arm length
• Dr = 2(pi)resistance arm length
• IMA = De/Dr
• You can cancel the 2(pi)
• Lever AMA
• The ratio of applied resistance force to applied effort force
• AMA = Fr/Fe
• The IMA is larger than the AMA because one measures the force and the other measures the distance
• Efficiency
• In a machine, the ratio of useful energy output to the total energy input, or the percentage of the work input that is converted to work output
• The ratio of AMA to IMA
• Efficiency = AMA/IMA
• The efficiency of a car is around 40% or less