Need Help from Physics
PostPosted: Thu Nov 30, 2006 9:24 pm
by Lyrical
The cable AB keeps the 8-kg collar A in place on the smooth bar CD. The y axis points upward. Determine the distance s from C to the collar A for which the tension in the cable is 150N.
location of:
B: (0m, 0.5m, 0.15m)
C: (0.4m, 0.3m, 0m)
D: (0.2m, 0m, 0.25m)
collar A's location is unknown. The required is the distance between C and collar A.
For an easier look, go here.
http://img86.imageshack.us/img86/4710/392ij8.jpg
PostPosted: Mon Dec 11, 2006 8:41 am
by Agent Anderson
I'd say I wish I'd seen this earlier, but I would have struggled with how to handle the normal force on the collar, and would probably not have been much help.
After a search, I saw you also posted this a Yahoo question, which had the smart response of taking the dot product of the vector force of gravity in the direction vector of the bar.
After that, I would personally take the route of summing the forces in each dimension, setting equal to zero, and solving for the x,y, and z of the collar.
PostPosted: Tue Dec 12, 2006 12:08 am
by Dante
I looked at it earlier, could have possibly solved it, but this has been up a while. More of a math problem really than a physics problem if you ask me. Still, the problem should be simpler if you move the coordinate axis so that the lowest x,y,z value happens to be set to zero. This can be made even simpler I imagine (to an extent) by using the rotation matrices to rotate the system about your y axis such that two of the points lie in the y-x plane... Still even these don't simplify it to an easy problem... sorry doesn't look like there are any easy buckets on this one, if you really want to work it out your just going to have to drudge through the algebra and expect that you'll make mistakes... If your teacher grades on physics, you'll likely get most of the points... if they grade on algebra, it may not be worth the time.
-Pascal
