A Quick Lesson In Understanding Free Fall And Air Resistance

Everyone knows what gravity is — it is the force that pulls people, objects, and anything and everything back to Earth. It is also what keeps the planets in orbit, so we don't float freely into space. But given how physics aims to study how everything works, it is no surprise that it also has given birth to concepts related to gravity, namely free-fall motion and air resistance.

Free-fall motion and air resistance are two separate concepts used to explain how people and objects react to gravity. But despite their differences, they are intercorrelated because free-fall motion affects air resistance in specific ways.

What is free fall motion?

By definition, free-fall motion is when someone or something succumbs to gravity and gravity alone — when they fall without any force affecting their speed. According to physics, all kinds of matter, regardless of its size or mass, fall with the same acceleration rate if they are solely influenced by gravity — for example, free falling a car that weighs two thousand tons and a person weighing 75kg.

If you apply Newton's second law, the car — which is heavier — would reach the ground first since it experiences more force of gravity, and the amount of gravity is equivalent to the amount of acceleration. However, it is crucial to note that acceleration depends on both force and mass. The car that weighs 2000 tonnes has more mass than the person, and this increased mass has an opposite effect on the car's acceleration. As a result, the direct impact of greater force on the car that weighs 2000 tonnes is offset by the opposite effect of the greater mass. Meaning, both vehicle and person falls at an equal rate of approximately 10 meters per second.

How is it affected by air resistance?

The concept of free-fall motion is simply falling without taking into account air resistance. A falling object will always encounter air resistance in the natural world, which is the reaction when an object collides with air molecules. If an object, regardless of its mass, encounters more air resistance, its rate of acceleration as it falls is less than it should be.

The amount of air resistance that a falling object encounters depends on two factors — its speed and its cross-sectional area. To put it simply, if it has more speed, it will experience an increased amount of air resistance. Similarly, an increase in the cross-sectional area will also result in more air resistance.

Examples of free fall motion affected by air resistance

Take a look outside of your window. If you have trees in sight, pay close attention to how the leaves fall off its branch and to the ground. Since each leaf has a wide cross-sectional area, they fall with more air resistance, thus slowing its speed.

On the contrary, if you drop a ball from your window, the ball will fall relatively fast due to its small cross-sectional area. However, if you attach a parachute to it, it will fall slowly due to the large cross-sectional area of the parachute, which causes more air resistance.


Free-fall motion and air resistance may be two different concepts, but their differences make them react to one another — if an object or a person falls with a lot of air resistance, they will fall at a low speed. But if they fall without any resistance whatsoever, they will fall freely, hence the term.

There's so much more to this shared relationship to discover! To learn more about how physics applies to our everyday lives, enrol in physics tuition right away. From 'O' Level physics tuition to JC physics tuition to even International Baccalaureate physics studies — kick-start your physics journey and dive deep into the rewarding world of mind-blowing theories.