Free Body Diagram Homework: Forces to Consider

[dranseth]

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.

 

[slider142]

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.

 

[dranseth]

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?

 

[slider142]

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 F_t greater in magnitude than F_g, since F_t + F_g = F_net = ma and a must be non-zero, and I'm assuming the elevator is accelerating in the direction of F_t. ;)