Relationship between friction and weight

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SUMMARY

The relationship between friction and weight is established through the equation F=μN, where F represents the frictional force, μ is the coefficient of friction, and N is the normal force (weight). While the coefficient of friction remains relatively constant for specific material combinations, the frictional force increases proportionally with the normal force. This increase occurs because the contact surface area between materials expands as the normal force increases, primarily due to the deformation of surface asperities.

PREREQUISITES
  • Understanding of basic physics concepts, particularly forces and friction.
  • Familiarity with the equation of motion and Newton's laws.
  • Knowledge of material properties and surface interactions.
  • Basic comprehension of molecular structures and their impact on physical properties.
NEXT STEPS
  • Research the different coefficients of friction for various material combinations.
  • Explore the role of surface asperities in friction and wear mechanisms.
  • Study the effects of weight on friction in real-world applications, such as vehicle dynamics.
  • Learn about advanced friction models and their applications in engineering.
USEFUL FOR

Physics students, engineers, material scientists, and anyone interested in understanding the mechanics of friction and its practical implications in various fields.

j.2.3.6
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So I know that weight correlates with friction, as in more weight of an object means that it will experience more friction. However, what is not clear to me is why this occurs on a molecular level.

Thanks for the help
 
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j.2.3.6 said:
So I know that weight correlates with friction, as in more weight of an object means that it will experience more friction. However, what is not clear to me is why this occurs on a molecular level.

Thanks for the help

Welcome to the PF.

Actually, the coefficient of friction does not change much with the normal force (weight of an object). The retarding force due to that friction is proportional to the normal force, F=μN, but the value of μ does not change much for a given material combination.

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

.
 
To answer your question the reason why friction, to an approximation, depends on the normal force is because, for relatively small forces, the surface area in contact increases linearly with the normal force. The root cause of friction is due to asperities. As you can see in the image, as the asperities are compressed the surface area of contact increases.
 

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