Forces on Identical Bricks: Ranking Magnitudes

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SUMMARY

The discussion centers on the forces acting on three identical bricks pushed across a table at constant speed. Participants identified horizontal forces including push, friction, and interactions between the bricks. It was concluded that when the push force equals the friction force, the bricks maintain constant velocity due to the balance of forces, as described by Newton's first law. Understanding that a net force is required for acceleration or deceleration clarifies the mechanics at play.

PREREQUISITES
  • Newton's First Law of Motion
  • Newton's Second Law of Motion
  • Concept of net force
  • Understanding of frictional forces
NEXT STEPS
  • Study Newton's Laws of Motion in detail
  • Explore the concept of friction and its coefficients
  • Learn about free body diagrams and their applications
  • Investigate the relationship between force, mass, and acceleration
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Physics students, educators, and anyone interested in understanding the principles of motion and force dynamics.

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Three identical bricks are pushed across a table at constant speed as shown. Rank the magnitudes of all the horizontal forces that you identified in your free body diagram. So I identified the horizontal forces of push, friction, system a on system b, and b on a. I understand the force will equal 0 because they are moving at a constant speed and are equal and opposite. I am having trouble conceptualizing how if the force of the push is equal to the force of friction the blocks could possibly keep moving forever. If the force of the push equals the force of friction doesn't that mean it would stop moving because of friction??
 

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No, it means that there is a push force balancing the friction so that the object does not accelerate. In order to decelerate (slow down) an object there needs to be a net force on it according to Newton's second law and the friction would have to be larger than the push.
 
Orodruin said:
No, it means that there is a push force balancing the friction so that the object does not accelerate. In order to decelerate (slow down) an object there needs to be a net force on it according to Newton's second law and the friction would have to be larger than the push.

Oooooh that makes a lot of sense. Thanks a lot!
 
The answes lies in Newton's first law.
 

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