**Falling in Air**

When an object falls freely, the resultant force acting on it is **gravity**. It will make the object accelerate around 10m/s² close to the earth. We call this force of gravity “weight” and the acceleration “the acceleration due to gravity.” Therefore the above equation becomes:

weight (N) = mass (kg) x acceleration due to gravity (m/s²)

If the object is on the Earth, not falling, we use:

weight (N) = mass (kg) x gravitational field strength (N/kg)

When an object falls through a fluid (i.e. a liquid or a gas, e.g. air), the fluid exerts opposite forces on the falling object reducing its motion, for example **air resistance**. The faster the object falls, the greater the frictional force. Eventually, this would be equal to the weight of the object – this resultant force is now zero, so the object will stop accelerating and begin moving at a steady velocity – called the **terminal velocity**.

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