Simple and Compound Machines

A set of vocabulary flashcards covering the concepts of efficiency, mechanical advantage, and factors affecting machine performance based on the Week 3 General Science lecture.

Efficiency

A measure of how much of the energy put into a machine actually goes toward doing the job, rather than being wasted.

Input

The total energy or effort given to the machine.

Output

The useful work the machine does for the user.

Waste

The energy lost to factors like friction or heat.

Simple Machines

Machines with very few moving parts that usually have high efficiency due to less friction, such as a lever or a ramp.

Compound Machines

Machines made by connecting many simple machines together, such as a bicycle, which usually have lower efficiency due to friction at every connection.

Mechanical Advantage

A measure of how much a machine multiplies your force to make a task easier by spreading work over a longer distance.

Friction

The single biggest factor that reduces efficiency, occurring whenever two surfaces rub against each other and resist motion.

Lubricants

Substances like oil or grease used to reduce friction and raise the efficiency of a machine.

Heat (Energy Loss)

The form into which most wasted energy in machines turns due to friction; a machine feeling hot to the touch indicates it is less efficient.

Sound (Energy Loss)

Energy used to create clanking or whirring noises that is not going into moving the load.

Translational (Ramp)

Motion in a straight line where pushing energy is converted directly into potential energy with very little wasted heat.

Rotational (Pulley/Lever)

Motion involving a rotating wheel or bar where energy is lost to heat at a rubbing point such as an axle or fulcrum.

Work Input (Exercise Example)

The total work performed to push a crate up a ramp, which in the lesson example equals $2,000\,J$.

Work Output (Exercise Example)

The useful energy stored in a crate lifted to a height, which in the lesson example equals $1,500\,J$.

Car engine efficiency

A compound machine that is often only about $20\%$ to $30\%$ efficient because energy is lost to heat and friction among hundreds of moving parts.

Well-oiled pulley system efficiency

A simple machine that can reach an efficiency of approximately $95\%$.

AMA of 4

An Actual Mechanical Advantage indicating that the machine makes the load $4$ times lighter for the user to lift.