Tuesday, May 20, 2014

Tracker: Cheryltan student video frisbee motion

Tracker: Cheryltan student video frisbee motion


http://weelookang.blogspot.sg/2014/05/tracker-cheryltan-student-video-frisbee.html
physics of Frisbee motion
this model suggests the Frisbee motion is a non-uniform acceleration motion in both x and y direction.
https://www.dropbox.com/s/azhjb2q1vbhfc5a/Cheryltantracker_5model.trz
vx = 7.0 m/s
vy = 5.05 m/s
fx = -2.804E0*t^2+7.713E0*t-7.861E0
fy = 3.977E-1*t-4.819
author of video: Cheryltan
author of model: lookang

http://weelookang.blogspot.sg/2014/05/tracker-cheryltan-student-video-frisbee.html
physics of Frisbee motion
this model suggests the Frisbee motion is a non-uniform acceleration motion in both x and y direction.
https://www.dropbox.com/s/azhjb2q1vbhfc5a/Cheryltantracker_5model.trz
vx = 7.0 m/s
vy = 5.05 m/s
fx = -2.804E0*t^2+7.713E0*t-7.861E0
fy = 3.977E-1*t-4.819
author of video: Cheryltan
author of model: lookang



Mentoring



* I cannot open my .trz file even though I dragged it into tracker, it says it cannot be loaded. What should i do now?

weelookang
i think you fix it already

Introduction:

Screen Shot 2014-05-18 at 7.00.02 PM.png

I threw my frisbee at a big angle of attack such that it is flying at a high gradient, before falling back.


weelookang
in addition, i would use the actual tracker screen shot to illustrate, adds realism to your discussion.

frisbee_2014-05-20_0808.png

weelookang
nice idea to discuss the phases. even better if you can discuss the model to represent the motion as in my trz file
https://www.dropbox.com/s/azhjb2q1vbhfc5a/Cheryltantracker_5model.trz

Phases
Time
A to B (Maximum vertical displacement)
0-1.17s
B to B1 (Maximum horizontal displacement)
1.17-1.92s
B1 to C (Rest)
1.92-2.50s

Questions:Screen Shot 2014-05-18 at 6.44.26 PM.png
I do not understand why my acceleration values are all negative although I have already set the axes and right is the positive direction.

weelookang
the negative ax suggests the acceleration in the x direction is pointing to the left, so the motion is being slowed down in x direction, which make sense.

if ax is positive, that will mean the Frisbee will speed up in + x direction.


Should I obtain the acceleration values from the acceleration graphs themselves or from the velocity graphs? I am not sure because my acceleration graphs are quite haphazard.

weelookang
i got the results for ax and ay by analysing the following graphs and using the Analyse Curve Fits.
the results suggests the following:
ax = -2.804t^2+ 7.813t-7.861 (looks like a parabola so i use parabola fit)

ay = 0.3977t-4.819 (looks like a straight line to me)
frisbee+ax.png
frisbee+ay.png

Screen Shot 2014-05-18 at 6.44.36 PM.png

I don’t quite understand why my vertical acceleration graph is so constant. Shouldn’t there be some kind of decreasing acceleration when it is reaching point B?



weelookang
actually most free-fall object the ay = -9.81, constant value
the Frisbee data suggests the Frisbee is experiencing also a constant value of about -4.819.

what is interesting to note is the ax is actually a parabola power t^2, which is unusual, the video evidence suggests the motion is actually non-uniform acceleration in both x and y direction  

finally, if you can describe the motion using model (equations) like i have, you would be more like scientists!
can you try?
frisbee_2014-05-20_0808.png
frisbee_y_2014-05-20_0809.png

Thank you so much!!!!!


weelookang
enjoy!