Free Body Diagram Homework: Forces to Consider

AI Thread Summary
When drawing a free body diagram for an elevator, the primary forces to consider are the gravitational force (Fg) acting downward and the tension force (Ft) acting upward. If the elevator is accelerating upwards, Ft must be greater than Fg to account for the net force required for acceleration. The relationship between these forces is expressed as Ft + Fg = Fnet = ma, where 'a' is the acceleration. It's important to note that while the elevator may move upwards at a uniform velocity at times, the question specifies that it is accelerating. Therefore, the analysis of forces in this context is correct.
dranseth
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Homework Statement


When drawing a freebody diagram for just an elevator, not the people in it, what are all the forces that we have to consider? I just used Fg down and Ft up, but because it is accelerating up, I made Ft greater.
 
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Just because the elevator is moving up, doesn't mean it is always accelerating up. It may only accelerate when it first starts moving and right before it stops at your floor. Otherwise, it may be moving with uniform velocity upwards.
 
Well, in the question it stated that it was accelerating... So was I right to have only the two forces Ft and Fg with Ft bigger?
 
dranseth said:
Well, in the question it stated that it was accelerating... So was I right to have only the two forces Ft and Fg with Ft bigger?
In that case, your diagram is correct to have Ft greater in magnitude than Fg, since Ft + Fg = Fnet = ma and a must be non-zero, and I'm assuming the elevator is accelerating in the direction of Ft. ;)
 
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