Frictional force- sign convention

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SUMMARY

The discussion centers on the sign convention for frictional force in a horizontal spring-mass system. Participants agree that the frictional force is directed to the right when the mass is released from the extreme right position, opposing the motion towards the left. The confusion arises from the application of the work-energy theorem, where the frictional force is considered negative due to its opposition to the direction of motion. Ultimately, the consensus is that frictional force should be treated as negative when calculating work done against it.

PREREQUISITES
  • Understanding of Newton's laws of motion
  • Familiarity with the work-energy theorem
  • Knowledge of spring-mass systems
  • Basic concepts of friction and its effects on motion
NEXT STEPS
  • Study the work-energy theorem in detail, focusing on sign conventions
  • Explore the dynamics of horizontal spring-mass systems
  • Learn about the role of friction in mechanical systems
  • Investigate advanced topics in classical mechanics, such as energy conservation
USEFUL FOR

This discussion is beneficial for physics students, educators, and anyone studying mechanics, particularly those interested in the dynamics of spring-mass systems and the implications of friction on motion.

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Frictional force-- sign convention

For a horizontal spring mass system is the frictional force considered negative (-μmg)? i guess it will be negative; the minus sign used to convey the force is trying to impede the motion of block then with that guessing work; i think friction force will be always negative for a horizontal spring mass system. If I'm wrong please correct me :)
 
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IN a horizontal system, "+" usually means "to the right", and "-" means "to the left." Is your frictional force to the right or to the left?
 


jtbell said:
IN a horizontal system, "+" usually means "to the right", and "-" means "to the left." Is your frictional force to the right or to the left?

Appreciate your reply :)

The frictional force is to the right; the case under consideration is: when the mass is stretched to the extreme right and let it go, as the mass moves towards the left under spring action, the friction force will try to impede the motion hence to the right.. But while deriving the work energy theorem for the particular case the friction force is taken as negative.. hence I'm confused!
 


Work is positive when the force is in the direction of motion (both + or both - in the case of one-dimensional motion) and negative when the force is opposite the direction of motion (one + and the other -).
 


GOT IT! i made a mistake while calculation; i mistook force as +ve and negative whereas i was supposed to take the work due to frictional force negative :)

Thanks for your time jtbell. :) Really appreciate your help. :)
 

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