How much work was done by the tension in the cable?

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brncsfns5621
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I think I have been staring at this question too long as I can not figure it out. I am sure the answer is simple:

A 1500-kg elevator moves upward with a constant speed through a vertical distance of 25m. How much work was done by the tension in the cable?

I know that W= (F cos 0)s, and that F= ma. What I can't figure out is the acceleration. It doesn't have one as it is moving with a constant speed. Any info on where to start?
 
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F=ma when F is the total force on the object. Here, the total force is 0, since the object isn't accelerating, and so the tension in the cable must exactly balance the force of gravity.
 
Yea, if F is the total force on the object (you can always use F to stand for only one contribution to the force, it's just then F=ma won't hold).