Calculating Terminal Velocity for Parachute Design

[whisperblade]

This is my first time posting here but i need some serious help.

I'm in the process of doing a physics project right now, and I decided to relate the surface area of an object to its terminal velocity. I know how I am going to set up this experiment using coffee filters and string and a set weight to make sure the parachute goes down straight and all, but I'm at a loss at how to calculate the terminal velocity of the object. can someone please help!

 

[Pandemonium]

Most of the similar experiments I've seen is to use data loggers and motion sensors. That is the simplest way of finding the terminal velocity. However, if you don't have the luxury of such apparatus, you can always use the stopwatch method, measure the time taken over a vertical distance once the terminal velocity has been reached. The percentage uncertainty may be high due to human reaction time, but there are a few ways to reduce it. I leave it up to you to think of how that can be done.

 

[Adrian Baker]

We've done this succesfully as an A2 project. We used cut-down refuse sacks to make large parachutes. This way they fell slower and errors with timing by hand were minimised.

We dropped them down a four floor high stairwell. Terminal velocity was estimated as being reached by the time they had dropped one floor. Timing was from there to the ground.


A good investigation is to see what is the optimum size hole in the middle for slow and stable descent.

 

[whisperblade]

Well i understand to use the stopwatch method but let me know if I am setting this up right. My teacher refuses to help us.

I got the parachute things set up. And a set vertical height i can drop from. I am going to use a video camera to help play out the falling motion too. To calculate terminal velocity I basically find the velocity when i see that the parachute is traveling at a constant speed. But the thing is, on the syllabus I have it says i need to find a mathmatical relationship. So would that mean that I need to somehow relate surface area to the terminal velocity of the object.

 

[Adrian Baker]

Yes. What you say above sounds correct.

A good parachute design should hit terminal velocity pretty quickly.