Work done by friction on potted plant

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Homework Help Overview

The problem involves calculating the work done by friction on a potted plant being moved along a shelf. The context includes a 2.75-kg mass and a coefficient of kinetic friction of 0.549, with a specified distance of 1.07 m.

Discussion Character

  • Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • Participants discuss the calculation of normal force and frictional force, as well as the implications of sign conventions for work done by friction. There is debate over whether the work done by friction should be considered positive or negative based on different interpretations of the scenario.

Discussion Status

The discussion is ongoing, with participants exploring different interpretations of the sign conventions related to work done by friction. Some guidance has been offered regarding the relationship between the direction of forces and displacement, but no consensus has been reached on the correct sign convention.

Contextual Notes

Participants are considering the implications of sign conventions in the context of work done, particularly regarding the direction of forces relative to displacement. There is an emphasis on understanding how these conventions affect the interpretation of the results.

Lolagoeslala
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Homework Statement


A 2.75-kg potted plant rests on the floor. Determine the work required to move the
plant at a constant speed along the shelf for 1.07 m where the coefficient of kinetic friction is 0.549

The Attempt at a Solution


I found the Fn:

Fn = mg
Fn = 26.95 N

Ff = Fnμ
Ff = (26.95N)(0.549)
Ff = 14.79555 N

W = Ff x d
W = 14.79555 N x 1.07 m
W = - 15.8312 J

This would be negative correct?
 
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Well the work done by the frictional force would be positive due to sign conventions. So your answer would be W = + 15.8312 J, however the work done on the plant due to friction is W = -15.8312 J.


Your answer is correct, but the sign depends on the convention used.
 
I don't think you need a sign convention for this.

The angle between the applied force and the displacement is 0, so the work done by the applied force must be positive.

The angle between the frictional force and the displacement is 180, so the work done by the frictional force must be negative.
 
rock.freak667 said:
Well the work done by the frictional force would be positive due to sign conventions. So your answer would be W = + 15.8312 J, however the work done on the plant due to friction is W = -15.8312 J.


Your answer is correct, but the sign depends on the convention used.

would u like to expand?
 
Lolagoeslala said:
This would be negative correct?
You are asked for the work required to move the plant, i.e. the work done by the force that moves it. That force and the distance moved are in the same direction, so the product must be positive, no matter which way you assign the positive direction in the co-ordinate system. That is, either F and d are both negative or they're both positive, but Fd will always be positive.
 

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