Simplifying Assumptions

The world is complex. Every situation has many possible factors to take into account. Often however many of these possible factors are irrelevant and can be ignored. For example, we would not expect the temperature to greatly influence the acceleration due to gravity so can ignore this factor. Even if a factor cannot be ignored, we can often gain insight into a phenomenon by ignoring it. A model can later be refined by taking more factors into account not making that simplifying assumption.

The table below lists some common assumptions.



Friction is negligible


The motion of a car down or up a slope

No heat lost

Heat being transferred from one body to another when both are insulated together

Mass of string or spring is negligible

Simple pendulum

Mass on stretched spring

Resistor of ammeter is zero

Electric circuits

Resistance of voltmeter is infinite

Electric circuits

Internal resistance of battery is zero

Electric circuits

Conductor obeys Ohm's Law

Electric circuits

100% efficiency



Gas is ideal


Collision is elastic

Collisions. In fact perfectly elastic collsions are only possible between atoms and subatomic particles.