Cornell notes for 114-121 (Input and Output force (Input force is the…
Cornell notes for 114-121
Input and Output force
Input force is the force you exert on a machine
The input force moves the machine a certain distance called the input distance
Output force is the force a machine exerts on an object
the machine does work by exerting force over a certain distance called the output distance
if the amount of work that you do stays the same but the force drops then the distance has to increase. so if a machine allows you to do use less input force then you have to apply the input force over a greater distance.
A machines mechanical advantage is the number of times a machine increases the force exerted on it
MA= Output / Input
if you input 10N into a machine and the machine's output is 30N then the MA is 3
if you input 20N and the machine outputs 10N then the MA is 0.5
if only the direction changes in a machine then the MA will always be 1
Input and Output work
The output work is the output force times the output distance
Input work is the input force times the input distance
What is a machine?
A machine is a device that allows you to do work in a way that is easier and more effective.
Ex: inclined plane, lever, wheel and axle
They change the way in which work is done
you can exert more force over a shorter distance to make something go a longer distance
Ex: if you are riding a bicycle in high gear you are exerting more force over a shorter distance to have the bicycle move a longer distance
some machines don't change force or direction. like Pulleys, they make your job easier by changing the direction multiple times.
Ex: if you are trying to lift an 1000 pound weight you could use pulleys to make that easier.
Efficiency of machines
in the real world the output work of a machine is less than the input work.
in every machine some work is wasted overcoming friction
the less friction there is, the closer the output work is to the input work.
efficiency of a machine is the output work divided by input work times 100 and is expressed as a percent
all machines have an efficiency of less than 100% due to friction