Mechanical Systems

• machine: A device that helps us do work
• Archimedes screw: A device used to carry water up a tube, now used for grain

  
• Simple machine: A tool or device made of one basic machine
• What are the 6 simple machines?

  lever, screw, inclined plane, wheel and axle, pulley, and wedge
• Lever: rigid bar that rotates around a fixed point (fulcrum/pivot). Reduces force needed to carry out actions like pulling stuff out or moving large loads.
• To move a large load, you must move a greater distance than the load does
• Levers are classified in three classes; first class, second class, and third class.
• First class lever: fulcrum is between the load and point of effort. FULCRUM IN THE MIDDLE

  
• Second class lever: load is between fulcrum and effort. LOAD IN MIDDLE

  
• third class lever: effort/force is between the load and the fulcrum. FORCE IN MIDDLE

  
• Inclied plane: a ramp to lift heavy objects upward. There is less force, but greater distance and the steeper the angle, the harder it is control movement.
• Wedge: A triangle shaped object used to seperate, lift, or hold an object in place. Force is applied to the base, funneling down to the narrow end. Force applied is increased and so is the distance in object
• Screw: Cylinder with grooves cut in a spiral shape. Increases force used.Converts rotational motion to a linear one
• Pulley: A device consisting of a wheel with a rope or chain passing through a hole in its center. Each wheel added splits the force evenly
• Wheel and axle: two wheels of different sizes that turn together. Increases the size of force, but needs a greater distance to apply force
• Complex machines have subsystems;linkages and transmissions in mechanical devices
• Linkage: Transfers energy from source to object
• Transmission: A type of linkage that transfers energy from an engine to the wheels. contains a number of gears
• Gears work together in gear trains (2+ gears). The gear with force applied from the outside is the driving gear, which applies force to the driven gear
• If the driving gear is larger than the driven gear, the turning speed will increase. These are called multiplying gears
• If the driving gear is smaller than the driven gear, the turning speed will decrease. these are called reducing gear
• mechanical advantage (MA or force ratio) =output force (N) / input force (N)
• The more times a machine multiplies force, the higher the mechanical advantage
• what are some examples of first class levers?


  pliers, scissors, crow-bar, see-saw, nail clippers, tongs, hammer
• What are some examples of second class levers?

  wheel-barrow, Nutcracker, stapler, doors/gates, bottle openers, nail clippers
• What are some examples of third class levers?

  fishing rod, broom, baseball bat, bow and arrow, jaw,
• Speed ratio: a measure of how the speed of the object is affected by a machine
• Speed ratio (SR) = input distance (m) / output distance (m) OR

  SR = D(distance) x input / D x output
• Input force: The force applied to a machine
• Input distance: the distance that input force is applied
• Output force: the force the machine applies to the object
• Output distance: the distance made from the output force that is applied
• When you are using a machine, the distance travelled with the force you expert will be greater than the distance the load will move
• Mechanical advantage: the amount a machine can multiply a force
• Speed ratio: a measure of how the speed of the object is affected by a machine
• Mechanical advantage and efficiency is affected by friction, speed ratio is not
• Efficiency: a measurement of how well a machine or device uses energy. Some energy will be lost due to heat or friction. The more energy lost, the less efficient it is.
• Efficiency (%) = MA/SR x 100
• Work: force acting on an object to make it move. No movement completed = no work
• Work (W) = Force (N) x distance (m)= Nm or J