## Monday, September 28, 2015

### Tracker Skydiving Model At which point in Fig.1 A, B, C or D is the parachute fully open?

Tracker Skydiving Model At which point in Fig.1 A, B, C or D is the parachute fully open?

## My Tracker Analysis

The motion can be classified into 5 sections

## 1. falling under gravity and drag force with parachute closed

model: vy = if(t<15,-1.230E-1*t^2+5.454E0*t+1.146E0,0)
in English, it means the parachutist is falling at |vy| = -0.123*t^2+5.454*t+1.146 m/s starting from t = 0 to 15 s

## 2. constant velocity with gravity=drag with parachute closed

model: vy = if(t<15,0,if(t<57,55,0))
it means the parachutist is falling at |vy| =57 m/s from t = 15 to 57 s in the video

## 3.constant deceleration with parachute opening

model: vy = if(t<57,0,if(t<63.5,-5.934E0*t+3.932E2,0))
it means the parachutist is falling at |vy| = - 5.934*t +393 m/s from t = 57 to 63 s in the video

## 4.  constant deceleration with parachute fully opened

model: vy = if(t<63,0,if(t<71,-1.221E0*t+9.313E1,0))
it means the parachutist is falling at |vy| = - 1.22*t +93.13 m/s from t = 63 to 71 s in the video

## 5. constant velocity with parachute fully opened

model: vy = if(t<72,0,5.6)
it means the parachutist is falling at |vy| = 5.6  m/s from t = 63 to 71 s in the video

## answer is C

From the video by Discovery Channel, it suggests that indeed as Mr Tan post on his blog, the answer for  parachute fully open is actually closer to C, instead of B as stated in Cambridge Marker's Report for the paper.
One up for peer review and open discussion. Thanks to Mr Tan's post!

 from http://tankimkia.blogspot.sg/2015/09/the-physics-of-skydiving-explain-with.html