How Do You Calculate Frictional Force on a Block?

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SUMMARY

The calculation of the frictional force on a 10-lb block subjected to a 3-lb horizontal force on a rough surface involves understanding static and kinetic friction coefficients. Given a static friction coefficient (\mus) of 0.5 and a kinetic friction coefficient (\muk) of 0.4, the maximum static friction force is calculated as 49.0 lb, which is approximately 22N. Since the applied force is 3-lb (approximately 1.4N), the frictional force opposing the motion equals the applied force, confirming that the block remains at rest under these conditions.

PREREQUISITES
  • Understanding of Newton's laws of motion
  • Knowledge of static and kinetic friction coefficients
  • Ability to perform unit conversions between pounds and Newtons
  • Familiarity with basic mechanics equations such as FN=mg and Fk=\mukFN
NEXT STEPS
  • Study the implications of static versus kinetic friction in different scenarios
  • Learn about the effects of surface texture on frictional forces
  • Explore advanced topics in mechanics, such as friction in inclined planes
  • Investigate real-world applications of friction calculations in engineering
USEFUL FOR

Students in physics or engineering courses, educators teaching mechanics, and professionals involved in material science or mechanical design will benefit from this discussion.

mdawg467
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Homework Statement


A 3-lb horizontal force is applied to a 10-lb block on a rough horizontal surface. The block is initially at rest. If \mus is 0.5 and the \muk is 0.4, the frictional force on the block is?


Homework Equations


FN=mg
Fk=\mukFN
Fs,max=\musFN


The Attempt at a Solution


I found \mus,max required to move the 10-lb block was 49.0 lb/ms^2..or approximately 22N.

Since the force being applied is 3-lb, or approximately 1.4N, then the frictional force must be equal to the force being applied correct?

Thanks.
 
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mdawg467 said:

Homework Statement


A 3-lb horizontal force is applied to a 10-lb block on a rough horizontal surface. The block is initially at rest. If \mus is 0.5 and the \muk is 0.4, the frictional force on the block is?


Homework Equations


FN=mg
Fk=\mukFN
Fs,max=\musFN


The Attempt at a Solution


I found \mus,max required to move the 10-lb block was 49.0 lb/ms^2..or approximately 22N.

Since the force being applied is 3-lb, or approximately 1.4N, then the frictional force must be equal to the force being applied correct?

Thanks.

Sounds good - especially in America where apparently the pound is a unit of Force, not a unit of mass.
 
Thank you!
Yeah only here in America haha..
 

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