# Physics - Free Fall

> Source: https://ollybritton.com/notes/a-level/physics/topics/free-fall/ · Updated: 2020-10-11 · Tags: physics, school, year-1

##### What's another name for air resistance??
Drag.

##### What is the difference between air resistance and drag??
Drag is applicable to fluids other than air.

##### What are the three questions that you should ask at each stage of free fall??
* What are the forces?
* What is the resultant force?
* What is happening?

##### What's an easy way to remember the three questions you ask at each stage of free fall??
Forces, resultant, result.

##### A skydiver has just left a plane. What are the 5 stages of their journey??
* Leaving the plane
* Speeding up
* Terminal velocity
* Parachute opening
* Terminal velocity

##### Following the forces, resultant, result pattern, what's happening when a skydiver leaves a plane??
* __Forces__: The only force actinag is weight downwards
* __Resultant__: There's a large resultant force downwards
* __Result__: Accelerates downwards at $9.81ms^{-2}$

##### Following the forces, resultant, result pattern, what's happening when a skydiver is speeding up after leaving the plane??
* __Forces__: Weight downwards and drag acting upwards
* __Resultant__: Resultant force decreases, though still downwards
* __Result__: Acceleration decreases

##### Following the forces, resultant, result pattern, what's happening when a skydiver reaches terminal velocity for the first time??
* __Forces__: Drag is equal in magnitude to weight
* __Resultant__: Resultant force is zero.
* __Result__: Terminal velocity, zero acceleration

##### Following the forces, resultant, result pattern, what's happening when a skydiver's parachute opens??
* __Forces__: Drag increases as parachute opens
* __Resultant__: Large resultant force upwards
* __Result__: Speed decreases, large decceleration

##### Following the forces, resultant, result pattern, what's happening when a skydiver reaches terminal velocity for the second time??
* __Forces__: Drag decreases as speed decreases
* __Resultant__: Resultant force is zero.
* __Result__: Terminal velocity, zero acceleration.

##### If you have a skydiver with no parachute and a skydiver with an open parachute, which is experiencing the most drag??
The skydiver without a parachute.

##### Why does a skydiver without a parachute experience more drag than one with a parachute??
* Drag increases with speed
* Skydiver without a parachute is moving faster

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