Physics - Free Fall
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