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| Subject:
PHYSICS
Category: Miscellaneous Asked by: mocha28-ga List Price: $2.00 |
Posted:
29 Nov 2005 19:52 PST
Expires: 18 Dec 2005 20:08 PST Question ID: 599271 |
Reversing the algebraic sign on the velocity reverses the direction of motion. Is the same statement true for the acceleration vector and explain your reasoning? |
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| There is no answer at this time. |
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| Subject:
Re: PHYSICS
From: muehlbauer-ga on 30 Nov 2005 01:12 PST |
Absolutely. If you designate the "right" as a positive direction, and the "left" as the negative direction, than something traveling at +5m/s is traveling at 5m/s to the right. Add on that that object is accelerating at +5m/s^2, and it is accelerating to the right, or getting faster. Now, take this same object traveling at +5m/s, and say that it is accelerating at -5m/s^2. What is happening? The object is slowing down. Even though it is still traveling to the right, its acceleration is to the left. Carry this through further - one second after this statement is made, the object has stopped. It was going at 5m/s, accelerated at -5m/s^2 in the opposite direction, and is now at a stand-still. Carry this through yet another second further, and the object is traveling at -5m/s (5m/s to the left). Why? It is accelerating in the negative direction. This means that it is slowing down while its velocity is positive, and speeding up in the negative direction while the velocity is zero or negative. |
| Subject:
Re: PHYSICS
From: philnj-ga on 30 Nov 2005 11:37 PST |
muehlbauer-ga is pretty much right, but let me clarify. Reversing the algebraic sign of acceleration *DOES NOT* reverse the direction of motion. Reversing the algebraic sign of acceleration *DOES* reverse the direction of acceleration. If a body is traveling in a positive direction (positive velocity) has a negative acceleration, that means it is slowing down. Eventually, it will stop and begin traveling in a negative direction. v = at + v0; where v is instantaneous velocity; v0 is initial velocity, t is time and a is acceleration. v can be positive if a is negative when v0 > -at. When t >= -v0/a then the direction of travel becomes negative. |
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