Help with the work done problem

[jeevankasin]

Hi,

Some confusion with the attached problem. Some of us say that the work done on the load is W(x+y) while some others are saying that the WD on the load is just Wy since the motor moves the distance x and that work is done by the motor.

Could we have some clarifications?

Din

 

[berkeman]

Hi,

Some confusion with the attached problem. Some of us say that the work done on the load is W(x+y) while some others are saying that the WD on the load is just Wy since the motor moves the distance x and that work is done by the motor.

Could we have some clarifications?

Din

Welcome to the PF.

What are your arguments in favor of each choice?

 

[jeevankasin]

Option (A): One of us argues, since that is the distance the object moves, the WD should be that distance.

Option (B): The WD here is to bring the load up by a dist of y and multiplied by the force acting on it, which is the weight.

Force x Dist moved in the direction of the force

Option (D) : Since the object moves a horizontal distance of x followed by the vertical distance y, thus it W(x+y).

 

[SammyS]

What's the definition of work?

Do the relative directions of displacement and force matter?

 

[Nickie]

,

Thank you for reaching out and seeking clarification on this problem. The concept of work done can be confusing, so I am happy to provide some clarification.

In this scenario, both answers are technically correct depending on how you define the system and the work being done. Let me explain further:

First, let's define the system. In this problem, the system consists of the motor and the load. The motor is doing work on the load by moving it a distance x. However, the load is also moving a distance y due to external forces acting on it. So, in this case, the work done on the load can be calculated as W(x+y). This takes into account both the work done by the motor and the work done by external forces on the load.

On the other hand, if we only consider the work done by the motor, then the answer would be Wy. This is because the motor is only responsible for moving the load a distance x, and the external forces are responsible for the additional distance y. In this case, we are only looking at the work done by the motor, not the total work done on the load.

So, in summary, both answers are correct depending on the perspective and definition of the system. I hope this helps clarify the confusion. Please let me know if you have any further questions.