Work Due to Gravity: Negative, Positive, or Zero?

In summary, the sign of work done by gravity when walking down a flight of stairs is positive because the gravity force points in the same direction as the displacement. This is because the equation reduces to w=Fs.
  • #1
rent981
20
0
1. If your are walking down a flight of stairs would the sign of work be negative, positive or zero?



2. Well work =FCOS Theta Delta X.


3. SO I think it would be negative. My reasoning is that the normal force of the person walking down a flight of stairs is in the opposite direction of the gravitational force, so the result is negative work. Does this logic sound correct?
 
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  • #2
rent981 said:
1. If your are walking down a flight of stairs would the sign of work be negative, positive or zero?



2. Well work =FCOS Theta Delta X.


3. SO I think it would be negative. My reasoning is that the normal force of the person walking down a flight of stairs is in the opposite direction of the gravitational force, so the result is negative work. Does this logic sound correct?
I don't know about the logic, but the question is poorly worded. Are they looking for the work done by you, or the work done by gravity, or the total work done? You've put a different twist on it...solving for the work done by the normal force...which , confusingly, is actually 0 since the normal force doesn't move.
 
  • #3
The question states what is the sign of the work done by gravity not the person, sorry for the confusion.
 
  • #4
rent981 said:
The question states what is the sign of the work done by gravity not the person, sorry for the confusion.
Well then if you are looking for the work done by gravity on the person, the gravity force points down, and the displacement of that force is also down, so the work done by gravity is, to repeat the question, plus minus or zero??!
 
  • #5
Well if the forces are pointing in the same direction the sign of work would be positive. Because the equation would reduce to w=Fs.
 
  • #6
rent981 said:
Well if the forces are pointing in the same direction the sign of work would be positive. Because the equation would reduce to w=Fs.
Yes, correct. Gravity does positive work in this case, and you do negative work. That's why I don't climb up stairs too often, but I'll climb down a few floors or so once in awhile:wink:
 
  • #7
hehe nice. Thanks for your help. I understand this concept a lot better now!
 

Related to Work Due to Gravity: Negative, Positive, or Zero?

What is work due to gravity?

Work due to gravity is the amount of energy required to move an object against the force of gravity. It is a measure of the force applied to an object over a certain distance.

How is work due to gravity calculated?

The calculation for work due to gravity is W = Fd, where W is work, F is the force of gravity, and d is the distance the object is moved.

What is negative work due to gravity?

Negative work due to gravity occurs when the force applied to an object is in the opposite direction of its motion. This means that the object is moving in the direction of decreasing gravitational potential energy.

What is positive work due to gravity?

Positive work due to gravity occurs when the force applied to an object is in the same direction as its motion. This means that the object is moving in the direction of increasing gravitational potential energy.

What is zero work due to gravity?

Zero work due to gravity occurs when the force applied to an object is perpendicular to its motion. This means that the object is not moving in the direction of either increasing or decreasing gravitational potential energy.

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