Intuitive explanation of why work done by tension is 0?

In summary, the conversation discusses the concept of net work done by tension in a system involving two masses connected by a rope and a pulley. The solution involves using equations and the intuitive explanation given is that for a constant force, work is equal to force times displacement, and in a system with equal and opposite forces and equal displacements, the net work done by tension would be zero. This can be generalized to variable forces using integrals.
  • #1
navneet9431
Gold Member
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Homework Statement


IMG_20180821_092520.jpg


Homework Equations


Work Done=Force*Displacement in the direction of the force

The Attempt at a Solution


I tried to solve the problem this way,
I wrote these equations for the two masses,
T-mg=ma...(i)
Mg-T=Ma...(ii)
From (i)&(ii), T=[M(g-a)+m(a+g)]/2
and then I would multiply them with the displacement to get the net work done 0.
So this is how I solved it mathematically.
Can you please provide an intuitive explanation of why the net work done by tension would be zero?
I will be thankful for help!
 

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  • #2
navneet9431 said:
Can you please provide an intuitive explanation of why the net work done by tension would be zero?
Suppose you have two tug-of-war teams pulling on a rope and both teams are at a standstill. What work is being done?
 
  • #3
But the pulley is not standstill.right?
phinds said:
Suppose you have two tug-of-war teams pulling on a rope and both teams are at a standstill. What work is being done?
 
  • #4
navneet9431 said:
But the pulley is not standstill.right?
OK, suppose one team walks forward at 2mph and the other team walks backwards at 2mph, it which case the tension is unchanged. How much work does the tension do?
 
  • #5
navneet9431 said:
provide an intuitive explanation of why the net work done by tension would be zero?
For a constant force, work = force times displacement.
In a tug of war, equal and opposite forces, equal displacements. Fd+(-F)d=0.
For the pulley set up in the diagram, equal forces, equal and opposite displacements. F.d+F(-d)=0.
Easy to generalise to variable forces using integrals.
 
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  • #6
haruspex said:
For a constant force, work = force times displacement.
In a tug of war, equal and opposite forces, equal displacements. Fd+(-F)d=0.
For the pulley set up in the diagram, equal forces, equal and opposite displacements. F.d+F(-d)=0.
Easy to generalise to variable forces using integrals.
Thanks!
It was easy to understand.
 

Related to Intuitive explanation of why work done by tension is 0?

1. What is work done by tension?

The work done by tension is the amount of energy transferred when an object is moved by a force applied through a flexible medium, such as a rope or a string. It is measured in joules (J).

2. Why is the work done by tension sometimes 0?

The work done by tension can be 0 when there is no displacement of the object in the direction of the tension force. This means that the object is not moving or the tension force is perpendicular to the displacement, resulting in no work being done.

3. Can the work done by tension be negative?

Yes, the work done by tension can be negative if the object is moving in the opposite direction of the tension force. This means that the tension force is doing work against the motion of the object, resulting in a decrease in energy.

4. How does the angle between the tension force and displacement affect the work done?

The angle between the tension force and displacement affects the work done by tension through the calculation of the cosine of the angle in the formula W = Fd cosθ. When the angle is 90 degrees, the cosine is 0, resulting in no work done. As the angle decreases, the work done also decreases.

5. What is an intuitive explanation for why work done by tension is 0 when an object is at rest?

When an object is at rest, there is no change in its position or displacement. This means that there is no movement in the direction of the tension force, resulting in no work being done. The tension force may still be present, but without any displacement, there is no transfer of energy and the work done by tension is 0.

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