What is the direction of work in this figure?

In summary: Tension in itself is not a force, it is technically a tensor that gives you a force depending on which object you are drawing the FBD for. If you are drawing the FBD for the person, then the force resulting from the tension is directed to the right (it is the tension in the rope multiplied by the direction of the rope away from the object you are drawing the FBD for).
  • #1
patric44
296
39
Homework Statement
find the direction of work in this figure ?
Relevant Equations
w= F.d
iam not sure of the direction of work , is it positive becouse pulleys change the direction of the force ? or is it negative because of the arrow that indicates the direction of acceleration ??!
 

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  • #2
The work done by what force on what object? Your drawing does not look like a proper free-body diagram. A FBD should involve only one object and all of the external forces acting on this object.
 
  • #3
the work done by the person to lift that mass , this diagram is an exact replica to the example
 

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  • #4
patric44 said:
the work done by the person to lift that mass
There is no such thing. There is the "work done by the person on the mass". That work is positive because the force by the person on the mass (or rather, the rope) is in the same direction as the displacement when the mass is lifted. Then there is the "work done by the mass on the person", which would be the opposite because it is the same displacement but the force is the Newton 3 pair of the force of the person on the mass, i.e., it is equal in magnitude and opposite in direction.
 
  • #5
Orodruin said:
There is no such thing. There is the "work done by the person on the mass". That work is positive because the force by the person on the mass (or rather, the rope) is in the same direction as the displacement when the mass is lifted. Then there is the "work done by the mass on the person", which would be the opposite because it is the same displacement but the force is the Newton 3 pair of the force of the person on the mass, i.e., it is equal in magnitude and opposite in direction.
so the person work on the mass is + , but i have a question here what is the arrow in front of the person indicates , its some how strange that its opposite to the tension force ? as if its indicating the acceleration of the system indicating a negative work or something ?!
 
  • #6
patric44 said:
so the person work on the mass is + , but i have a question here what is the arrow in front of the person indicates , its some how strange that its opposite to the tension force ? as if its indicating the acceleration of the system indicating a negative work or something ?!
Tension in itself is not a force, it is technically a tensor that gives you a force depending on which object you are drawing the FBD for. If you are drawing the FBD for the person, then the force resulting from the tension is directed to the right (it is the tension in the rope multiplied by the direction of the rope away from the object you are drawing the FBD for). You should forget you ever saw that figure, it is a very bad figure that just seems designed to confuse.
 

1. What is the direction of work in this figure?

The direction of work in this figure refers to the overall movement or orientation of the objects or processes depicted in the figure. It can also refer to the direction of force or energy being applied.

2. How is the direction of work determined in a figure?

The direction of work is typically determined by the orientation of arrows or other symbols in the figure, as well as the context and purpose of the figure. In some cases, it may also be explicitly stated in a figure legend or caption.

3. Can the direction of work change in a figure?

Yes, the direction of work can change in a figure depending on the specific scenario or situation being depicted. For example, if the figure is showing a process or system over time, the direction of work may change as the process or system evolves.

4. Why is the direction of work important in scientific figures?

The direction of work is important in scientific figures because it can provide key information about the underlying mechanisms or processes being studied. It can also help to convey the overall flow or progression of events in a clear and concise manner.

5. Are there any common misconceptions about the direction of work in figures?

One common misconception about the direction of work in figures is that it always follows a linear or straight path. In reality, the direction of work can be complex and multidirectional, depending on the specific scenario being depicted.

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