Exploring Rolling Resistance: N+Ft or Separate?

In summary: It's okay to say that you must apply a moment (Mo=Fo*rd) that will overcome N*f in order to have just pure rolling. However, you have to be careful that force Fo=Mo/rd has to be ≤μstatic*N (cause it will cause additional slipping, something like...).
  • #1
LLT71
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http://imageshack.com/a/img923/733/FJKAqj.jpg
so here is the deal. is rolling resistance N+Ft or are they "separate" in a means of: N part is for static friction = mu*N and Ft is part of rolling resitance=coefficient of rolling resistance*Ft so that in order for tire to start rolling without slipping do I need to apply such force that overcomes Ft*coeff of rolling resistance. but at the same time that applied force has to be less than mu*N?
2. is N equal for every point from point C to B (see picture) and why?
3. why its the point of most interest just point B (like in this picture, and similar ones explaining rolling friction)?
 
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  • #2
LLT71 said:
http://imageshack.com/a/img923/733/FJKAqj.jpg
so here is the deal. is rolling resistance N+Ft or are they "separate" in a means of: N part is for static friction = mu*N and Ft is part of rolling resitance=coefficient of rolling resistance*Ft so that in order for tire to start rolling without slipping do I need to apply such force that overcomes Ft*coeff of rolling resistance. but at the same time that applied force has to be less than mu*N?
2. is N equal for every point from point C to B (see picture) and why?
3. why its the point of most interest just point B (like in this picture, and similar ones explaining rolling friction)?
See if section 4.1 of https://www.physicsforums.com/insights/frequently-made-errors-mechanics-friction/ helps.
 
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  • #3
I"m not sure how you calculate rolling resistance from that diagram. Part of rolling resistance is due to hysteresis, and part due to sliding friction. The force during radial deformation is greater than the force during recovery, lost to heat (hysteresis). There's also loss due to deformation along and across the tread, some of this loss is due to hysteresis, some due to sliding friction as the tread deforms and recovers.

The normal force at A and C is zero. The maximum normal force occurs near B.

Correction - the normal force at B and C is zero. The maximum normal force occurs near A.
 
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  • #4
rcgldr said:
I"m not sure how you calculate rolling resistance from that diagram. Part of rolling resistance is due to hysteresis, and part due to sliding friction. The force during radial deformation is greater than the force during recovery, lost to heat (hysteresis). There's also loss due to deformation along and across the tread, some of this loss is due to hysteresis, some due to sliding friction as the tread deforms and recovers.

The normal force at A and C is zero. The maximum normal force occurs near B.
say I am stupid but why forces at point A and C are zero? and how do I know whitch force I must apply to tire in order to roll it without slipping? what I must overcome with that force? so confusing... also, can you recommend me some books that explain tire kinematics? thank you!

@haruspex thank you!
 
  • #5
rcgldr said:
The normal force at A and C is zero. The maximum normal force occurs near B.
I think you have A and B swapped over relative to the diagram.
The maximum normal force should be right in the middle, no? But it will be greater a small distance x in front of that than at the same distance behind it.
 
  • #6
rcgldr said:
The normal force at A and C is zero. The maximum normal force occurs near B.
Correction - the normal force at B and C is zero. The maximum normal force occurs near A.
LLT71 said:
forces at point A and C are zero?
haruspex said:
I think you have A and B swapped over relative to the diagram.
I forgot the ordering of points in the diagram, I had thought it was A, B, C, right to left, not B, A, C right to left, so I got A and B swapped. I struck through the incorrect statement and added what should be a correct statement.

LLT71 said:
how do I know whitch force I must apply to tire in order to roll it without slipping?
It's complicated. You have hysteresis effects related to deformations along the sidewalls and across and in the direction of tread. There's also some sliding friction along the tread surface as it deforms, but according to wikipedia, most of the losses to heat are due to hysteresis.

http://en.wikipedia.org/wiki/Rolling_resistance
 
  • #7
rcgldr said:
It's complicated. You have hysteresis effects related to deformations along the sidewalls and across and in the direction of tread. There's also some sliding friction along the tread surface as it deforms, but according to wikipedia, most of the losses to heat are due to hysteresis.

http://en.wikipedia.org/wiki/Rolling_resistance

ok,and what about my picture in first post; is it decently okay if I say that I must apply moment (Mo=Fo*rd) that will overcome N*f in order to have just pure rolling but at the same time I have to be careful that force Fo=Mo/rd has to be ≤μstatic*N (cause it will cause additional slipping, something like burnout)?
 

FAQ: Exploring Rolling Resistance: N+Ft or Separate?

1. What is rolling resistance?

Rolling resistance is the force that resists the motion of a tire as it rolls on a surface. It is caused by the deformation of the tire and the friction between the tire and the surface.

2. How is rolling resistance measured?

Rolling resistance is typically measured in units of force, such as pounds or newtons. It can be measured using a rolling resistance testing machine, which applies a force to the tire and measures the resulting resistance.

3. What factors affect rolling resistance?

There are several factors that can affect rolling resistance, including tire design, tire pressure, tire size, tread pattern, and road surface. Factors such as weight, speed, and temperature can also impact rolling resistance.

4. What is the relationship between N+Ft and separate rolling resistance?

N+Ft, or combined rolling resistance, takes into account both the normal force (N) and the tangential force (Ft) acting on the tire. Separate rolling resistance refers to the individual components of N and Ft. The relationship between the two is that N+Ft is the sum of the separate rolling resistance forces.

5. Why is understanding rolling resistance important?

Understanding rolling resistance is important for various reasons. It can impact the fuel efficiency and performance of vehicles, as well as the wear and tear on tires. It also plays a role in determining the optimal tire pressure and choosing the right tires for different road conditions. Additionally, understanding rolling resistance can help in the development of more efficient and sustainable transportation systems.

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