mechanical systems study guide

fulcrum

supporting point of lever

load

output force, being moved or lifted

effort

input force

class one lever

fulcrum in the middle

class two lever

load in the middle

class three lever

• effort in the middle

• force advantage

• fulcrum is closer to load, meaning less effort is needed

longer effort arm

• easier to lift load

• load moves slower

short effort arm

• harder to lift load

• load moves faster

pulleys

• change the direction of force

• use gravity to help move load

• several pulleys reduce force to lift an object because spreads out weight

• force advantage

single fixed pulley

• more force

• heavier to lift

• less rope

block and tackle pulley

• less force

• uses more rope

• multiple movable pulley and multiple single fixed pulley

multiple pulleys

• more rope

• pulled a farther distance

• load requires less force

gears

• turn motion to force

• transfer energy

• driving gear (first one)

• force directed to driven gear (last one)

• follower gears are idler gears (middle ones)

gear train

more than two gears

wheel and axle

• two gears working together

• on a track

chain and sprocket

two gears with teeth that fit into links of a chain

odd number of gears

same direction

even number of gears

different direction

reducing force we use

force advantage

doing job faster

speed advantage

mechanical advantage

force ratio

force ratio

describes relationship between amount of output force to input force to move object over a distance

mechanical advantage formula

MA = FL/FE = load force (N) / effort force (N) = effort arm (M) / load arm

greater than one

force advantage

• effort lower

• speed and distance sacrificed

equal to one

no difference

• change in direction

less than one

speed advantage

• effort is greater

• load travels faster

• load travels further

work formula

Work = force x distance

types of energy

light, hydro, kinetic, potential, etc.

energy conversions

energy switches to different type in same object

energy transmission

same type of energy moves from one object to another

efficiency

• how much energy from machine was actually transferred to load

• stated as percent

• higher efficiency, better at transferring energy

• never a completely efficient machine because there is a loss of energy

boosting efficiency

adding lubricants (like grease) to reduce friction

efficiency formula

efficiency = work output / work input x 100%

inclined planes

• decrease amount of effort or force needed

• increase distance object needs to move

• same amount of work being done, work is easier though

work you do

input work

machine does on the load

output work

effect machine has on amount of work you do

• amount of work stays the same

• energy lost

ramp vs lifting straight up

• ramp increases amount of overall distance

• ramp reduces force

mass vs weight

• mass is amount of particles in an object

• weight is acceleration of gravity acting on mass

• 1.0kg = 9.81N

complex systems

• made up of simple machines and subsystems

• function to describe what the overall system is designed to do

linkage

when two levers are joined to change direction of force to make objects move

power transmission

changing one energy to another

Speed ratio

difference between the speed of two gears