Thread: Physics Quiz 10
View Single Post
  #20   Spotlight this post!  
Unread 26-11-2014, 12:00
dellagd's Avatar
dellagd dellagd is offline
Look for me on the field!
AKA: Griffin D
FRC #2590 (Nemesis) #2607 (The Fighting Robovikings)
Team Role: Mentor
 
Join Date: Sep 2011
Rookie Year: 2011
Location: PA
Posts: 890
dellagd has a reputation beyond reputedellagd has a reputation beyond reputedellagd has a reputation beyond reputedellagd has a reputation beyond reputedellagd has a reputation beyond reputedellagd has a reputation beyond reputedellagd has a reputation beyond reputedellagd has a reputation beyond reputedellagd has a reputation beyond reputedellagd has a reputation beyond reputedellagd has a reputation beyond repute
Re: Physics Quiz 10

Quote:
Originally Posted by Ether View Post
Yes, trackwidth is the distance between the 2 front wheels. (Or the 2 rear wheels). Here's an easy way to remember: It's the width of the "track" left by the vehicle when traveling forward in a straight line.
Ah, well even if I did find out the dimensions correctly I must have set up the proportion between the carpets velocity and the robot's orientation inversely. The solution below works out, so unless a mathematical equality that makes this give the right answer for the wrong reason is working here and I haven't realized what it is, I must have accidentally flipped that value somehow. It was late, I probably used the wrong angle for being tangential to the robots rotation which lead me to the wrong proportion.

Updated solution:
Spoiler for Solution:

2 + Vcy = Fy
Vcx = Fx
Fy/Fx = -2 / (28/12) #Known angle of vector sum/friction
Vcx/Vcy = 2 / (28/12) #Known angle of carpet velocity

Substitute in for Vcx and Fx:

2 + Vcy = Fy
(2 / (28/12)) * Vcy = (-(28/12) / 2) * Fy

Substitute in for Fy:

2 + Vcy = ((-2^2)/((28/12)^2)) * Vcy
Vcy = -1.153

Into another equation:

Vcx/(-1.153) = 2 / (28/12)
Vcx = -.988

Robot Velocity components are opposite of these.

Vry = 1.153
Vrx = .988

Vr = sqrt(1.153^2 + .988^2) = 1.519 ft/s

Vtangential = r * omega

r = d/2 = sqrt(2^2 + (28/12)^2)/2 = 1.537 ft

omega = Vt / r = 1.519 / 1.537 = 84/85 = .988 rad/s


I confirmed this using the other method and my answer was the same down to 6 decimal places.

__________________
Check out some cool personal projects in computers, electronics, and RC vehicles on my blog!

2016 MAR DCMP Engineering Excellence Award
2016 MAR Westtown Innovation in Control Award
2016 MAR Hatboro-Horsham Industrial Design Award
2015 Upper Darby District Winners - Thanks 225 and 4460!
2015 Upper Darby District Industrial Design Award
2015 Hatboro-Horsham District Winners - Thanks 2590 and 5407!
2014 Virginia Regional Winners - Thanks so much 384 and 1610, I will never forget that experience!
2014 Virginia Quality Award
2014 MAR Bridgewater-Raritan Innovation in Control Award
2014 MAR Hatboro-Horsham Gracious Professionalism Award
2013 MAR Bridgewater-Raritan Innovation in Control Award
2012 MAR Lenape Quality Award

Last edited by dellagd : 26-11-2014 at 12:39.
Reply With Quote