My physics teacher gave us a theoretical type of problem involving 3-dimensionl forces, though we've only studied 2-dimensional. I'm not exactly sure how they work, so can someone give me a little advise? The problem is:
You have 3 non net-zero forces acting on a particle located at the origin. F1 is in the positive z-plane. How can you make F2 and F3 (which are in and must stay in the x- & y-planes) so that the particle experiences no acceleration?
I'm assuming the particle will move, but we want to counteract the z-plane force with a net force so that the particle moves at constant velocity. Not sure how to do that though. Any ideas? Thanks.
2007-03-06 03:58:42 · 4 answers · asked by William W 1 in Science & Mathematics ➔ Physics
Using just x-y forces, it is not possible to cancel all the z force, as x-y forces have no component in the z direction. Any such force would be perpendicular to the z force. If the z force is not 100% in the z direction, then some of it could be cancelled, but any component in the z direction can be cancelled only by a force in that direction.
This is true in the x-y plane also. Imagine a particle moving on the x-axis at either constant speed or under acceleration. If it experiences then a force from the y direction only, how will the x directed speed change? Think about projectile motion. When a rock is thrown at some trajectory, its horizontal speed does not change (if it were done in a vaccuum). Only its vertical position is affected.
2007-03-06 04:31:10 · answer #1 · answered by David S 4 · 0⤊ 0⤋
A particle will experience acceleration if the net force acting on the object is non-zero, so I don't think this is possible given the situation you describe. Since 1 force is acting along the z-axis, and you other two forces must act on the x and y axes, the particle will always accelerate, I don't see any way around it.
2007-03-06 12:18:23 · answer #2 · answered by Pfo 7 · 1⤊ 0⤋
There must be more to the story.... Did you copy the entire question? Otherwise I think that is impossible. There is a law in mechanics called the law of compound motion (maybe it sometimes goes by another name) that explains why. Maybe you could search for information with "law of compound motion" as a key word.
Newton's laws of motion say that for acceleration to be zero, the object must be feeling balanced forces, or zero net force. The only way to cancel a force in the "positive z-plane" as you say would be with one that is pushing at least partially in the opposite direction "negative -plane"
2007-03-06 12:16:17 · answer #3 · answered by Christopher L 2 · 1⤊ 0⤋
You can resolve forces into x,y & z components in 3-d just like you resolve into x & y in 2-d
Zero acceleration implies zero net force for each component.
You have a mischevious physics teacher.
2007-03-06 12:21:27 · answer #4 · answered by lunchtime_browser 7 · 1⤊ 0⤋