Help (required force to move a sliding door weighing 100 kg with two rollers)

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Discussion Overview

The discussion revolves around calculating the required force to initiate the movement of a sliding door weighing 100 kg that operates on two rollers. Participants explore the forces acting on the system, including friction and potential rolling resistance, and seek clarification on the appropriate formulas to use.

Discussion Character

  • Technical explanation
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • One participant questions the concept of "rolling friction," suggesting that it may not apply since rolling surfaces do not move relative to each other, and instead introduces the idea of rolling resistance due to deformation.
  • Another participant computes the force required to move the door, using a coefficient of rolling friction and providing a detailed calculation that results in an estimated force of approximately 4 kg.
  • There is a discussion about whether bearings should be considered in the calculation, with one participant suggesting that rolling resistance might be more relevant than friction in this context.
  • A request for advice on computing the friction between the wheel and the axle is made, indicating a need for further clarification on the mechanics involved.

Areas of Agreement / Disagreement

Participants express differing views on the applicability of rolling friction versus rolling resistance, and there is no consensus on the best approach to calculate the friction between the wheel and axle. The discussion remains unresolved regarding the correct methodology for these calculations.

Contextual Notes

Participants mention inconsistencies in values for rolling friction from various sources, indicating that the values should only be used for approximate calculations. There is also uncertainty about the role of bearings in the system.

Who May Find This Useful

This discussion may be useful for individuals interested in mechanical engineering, physics, or anyone involved in designing or analyzing systems that involve rolling motion and friction. It may also benefit those seeking to understand the complexities of calculating forces in practical applications.

johnpaul
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what is the required force to start moving a sliding door weighing 100 kg with two rollers.
what are the forces acting on the system?

shall i used rolling friction on this?

what formula to use?

thanks a lot.
 
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Welcome to PF!

Hi johnpaul! Welcome to PF! :wink:

There's no such thing as "rolling friction", since a pair of rolling surfaces don't move with respect to each other.

There's rolling resistance, which is essentially energy lost due to deformation of the wheel, but I shouldn't think three's much of that with steel.

The main problem will be friction between the wheel and the axle though its centre. :smile:
 


tiny-tim said:
Hi johnpaul! Welcome to PF! :wink:

There's no such thing as "rolling friction", since a pair of rolling surfaces don't move with respect to each other.

There's rolling resistance, which is essentially energy lost due to deformation of the wheel, but I shouldn't think three's much of that with steel.

The main problem will be friction between the wheel and the axle though its centre. :smile:

But wouldn't the bearings be subject to rolling resistance as opposed to friction?
Maybe you assumed no bearings whereas I assumed bearings :-)
 
hi tim, hi molydood,

please correct me if I am wrong.

here's my computation:

Weight of door=100 kg
Number of wheels= 2
Weight per wheel =(100kg)/(2)= 50kg

F1= αW / r

F1- resistant force of a single wheel
α - coefficient of rolling friction
W - weight
r - radius (0.015m)

F1≈(0.0005 m)(50 kg) / (0.015 m)
F1≈ 1.67 kg; say 2kg

F''≈(F1)(2 wheels)
F''≈(2kg)(2 wheels)
F''≈4 kg

Force to move the 100 kg door horizontally:
F≈ 4 kg



Values for rolling friction from various sources are not consistent and the following values should only be used for approximate calculations.

Steel on Steel α = 0.0005m
 
hi,

can anyone advise me what is the proper way in computing the friction between wheel and the axle? its just a simple door carrier(please refer to the drawings above).

thanks
 

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