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Determining drag coefficient

  • Thread starter protossadv
  • Start date
  • #1

Homework Statement


I made a wind tunnel for a science project and i am trying to determine its windspeed.
I decided to suspend a pingpong ball on a string in the wind tunnel and measure the angle change.
But to do this i need to calculate the drag force and i cannot do this without knowing the drag coefficient of the ball.

Homework Equations


Drag force: 1/2*P*v2*A*Cd
x=vit + 1/2*at2

The Attempt at a Solution


One idea i have is to drop the same ball from a height and measure the time it takes to hit the ground.
I then use the equation x=vit + 1/2*at2 and solve for a.
Then, using 1/2*P*v2*A*Cd = ma, i solve for Cd, and use this drag coefficient to solve for wind velocity in the wind tunnel.
However, i think i cant simply put ma= drag force becuase this suggests that gravity equals drag force which would mean the ball was at terminal velocity.

How would you solve this?
 

Answers and Replies

  • #2
LowlyPion
Homework Helper
3,090
4
  • #3
for some reason i cant see whatever video or link you posted
can u show me the url?
 
  • #4
LowlyPion
Homework Helper
3,090
4
for some reason i cant see whatever video or link you posted
can u show me the url?
It's on Utube. Title: Lec 12 | 8.01 Physics I: Classical Mechanics, Fall 1999


I embedded it in the message. It plays for me just clicking it in the message.

Perhaps you will have better luck at Youtube?
 
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