Is friction related to velocity?

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Discussion Overview

The discussion revolves around the relationship between friction and velocity, particularly in the context of stirring a spoon in lemonade. Participants explore how friction and viscosity contribute to heat generation in fluids, as well as the factors influencing frictional forces.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants assert that friction does not depend on the velocity of the object but rather on the materials involved and the normal force acting on the object.
  • Others argue that while the frictional force itself is not affected by relative speed, the work done by that force—and consequently the heat generated—does depend on speed.
  • One participant questions whether the force of friction between the spoon and water contributes to an increase in temperature, suggesting that it does.
  • Another participant distinguishes between friction in solid surfaces and the resistance encountered by the spoon moving through water, stating that the latter does depend on speed.
  • Viscous forces are mentioned as analogous to friction in fluid systems, with implications for heat generation due to fluid-fluid and fluid-solid interactions.
  • There is a reference to Boltzmann's water churning experiment, which relates to the historical understanding of heat transfer and calorific fluid concepts.

Areas of Agreement / Disagreement

Participants express differing views on the relationship between friction and velocity, with some asserting no dependence while others highlight the role of speed in heat generation. The discussion remains unresolved with multiple competing perspectives.

Contextual Notes

There are limitations regarding the definitions of friction and viscosity, as well as the assumptions about the systems being discussed. The relationship between speed, friction, and heat generation is not fully clarified.

avito009
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I was mixing sugar in a glass of lemonade. As i stirred the spoon I thought that if I move the spoon faster it would cause the lemonade to heat up and thus increasing the temperature. Will the spoon cause heat to be generated in the lemonade? Also answer the title question.
 
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Friction does not depend upon velocity of the object but the material of the surface(over which object is moving) and the object, also friction depends upon the normal force N acting on the object by the surface.
Also on a microscopic level friction is caused by electrostatic forces between the object and the surface.

avito009 said:
I was mixing sugar in a glass of lemonade. As i stirred the spoon I thought that if I move the spoon faster it would cause the lemonade to heat up and thus increasing the temperature. Will the spoon cause heat to be generated in the lemonade? Also answer the title question.
Yes the temperature of te lemonade will rise up on continuous stirring, infact this was done by Boltzmann in his water churning experiment to obtain the relation between joules and calories. Where 1 Calorie = 4.186 Joules. This ultimately killed the myth of "calorific fluid" which was then used to explain transfer of heat.
 
The frictional force between two objects in not affected by their relative speed.
The amount of work done by that force (and hence the heat generated) is affected by their relative speed.
 
Is it the force of friction between the spoon and water?And does this friction cause an increase in temperature?
 
avito009 said:
Is it the force of friction between the spoon and water?And does this friction cause an increase in temperature?
Yes and yes.
 
The resistance encountered by the spoon moving through water is not the same as the friction between solid surfaces. It does depend on the speed.
.
 
Those are viscous forces that cause the heat inside this type of system, viscosity is ànalogous to friction in such system with a working fluid. Viscosity acts on fluid-fluid interaction and also fluid- solid interaction, according to the nature of viscous behaviour of the fluid, fluids are classified.
Also there can be fluid forces (flow energy) involved with the motion caused by agitation through the churning device.
 

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