Error measurement in time of flight tests

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Discussion Overview

The discussion revolves around measuring error in time of flight tests conducted with a potato cannon. Participants explore the implications of air resistance, wind effects, and the accuracy of timing measurements on the calculated height and velocity of the projectile. The scope includes experimental observations and theoretical considerations related to projectile motion.

Discussion Character

  • Experimental/applied
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant reports measuring the time of flight for a potato cannon and calculates an average time of 8.33 seconds, leading to a height estimate of 170m based on kinematic equations.
  • Another participant questions the impact of air resistance on the measurements and suggests that the accuracy of timing affects percent error.
  • A different participant clarifies that while wind does not affect gravity, it could influence the net force in the vertical direction.
  • One participant proposes that basic trigonometry might yield a better height estimate due to potential variations in acceleration if the projectile reaches terminal velocity.
  • Another participant argues that the projectile likely did not reach terminal velocity and notes the possibility of wind at higher altitudes, despite calm conditions at ground level.

Areas of Agreement / Disagreement

Participants express differing views on the effects of wind and air resistance, with no consensus reached on the accuracy of the height calculation or the significance of potential errors in measurement.

Contextual Notes

Participants acknowledge various assumptions, such as the neglect of air resistance and the conditions of wind at different altitudes, which may affect the accuracy of the measurements and calculations presented.

bassplayer142
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I build a potato cannon with my friend and we were having fun shooting it safely in a clearing. I decided to shoot is straight up and measure the time it is in air. Out of three measurements I got 9, 9, and 7 seconds which is a long time. Taking and average and Using 2 dim eqs I got 2v=at, v=40.875 for initial and final velocity, Then using vf^2=Vo^2 +2ax I got a height of 170m or about 558 feet. How much of a error could I expect to receive. It was at about 90 degrees and I figure if the wind is blowing horizontal then there would be no error considering that it wouldn't affect gravity. Thanks.
 
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Is there air resistance?
The percent error is also affected by the accuracy of the timing
 
also as you said,
bassplayer142 said:
I figure if the wind is blowing horizontal then there would be no error considering that it wouldn't affect gravity.

Even if the wind were blowing upwards at 5000m/s, gravity wouldn't be affected. What you meant to say is that it would not affect the net force in the y direction.
 
Velocity would be fairly accurate as to the height you'd be better doing some basic trig to figure out the height since you wouldn't really have constant acceleration if it hits it's terminal velocity.
 
I don't think it hit terminal velocity at all. Also, the day had relatively not wind at all, but that does not mean that there was wind at higher altitudes which there almost always is. 90mi/hr, it a large number and for this potato cannon, I'm just making sure it's near accurate. Keep in mind the measurements of time was taken from at average and is near exact. Thanks
 

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