A system of two bodies and wall

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SUMMARY

The discussion centers on the dynamics of a system involving two bodies, A and B, positioned against a smooth wall. Participants analyze the forces acting on both bodies, concluding that without upward friction, the system cannot remain in equilibrium if it starts at rest. The consensus is that both bodies will eventually slip and fall due to gravitational forces, with the absence of sufficient frictional forces to maintain their positions. Key concepts include free body diagrams, equilibrium conditions, and the role of friction in motion.

PREREQUISITES
  • Understanding of Newton's laws of motion
  • Familiarity with free body diagrams
  • Knowledge of static and kinetic friction
  • Basic principles of equilibrium in physics
NEXT STEPS
  • Study the application of Newton's laws in multi-body systems
  • Learn to construct and analyze free body diagrams for complex systems
  • Research the differences between static and kinetic friction and their implications in motion
  • Explore equilibrium conditions and how they apply to dynamic systems
USEFUL FOR

Physics students, educators, and anyone interested in understanding the mechanics of forces in multi-body systems, particularly in contexts involving friction and equilibrium.

  • #31
rudransh verma said:
There have to be relative motion between A and B for the friction to occur here.
No. That's only true for kinetic friction. I will add to @haruspex's comment...

Suppose a small parachute is attached to block B. Since A and B are pressed together, there could be enough static friction to prevent them sliding relative to each other. A and B would then fall together (in the same way as if they were stuck together).

Of course If you use a sufficiently big parachute and A is very heavy, then A will fall faster than B. Sliding occurs between A and B and the friction is kinetic.
 
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  • #32
Steve4Physics said:
No. That's only true for kinetic friction. I will add to @haruspex's comment...
O yeah! But there is also no static friction here because of the absence of any upward force. Both will fall as one system.
 
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  • #33
rudransh verma said:
O yeah! But there is also no static friction here because of the absence of any upward force. Both will fall as one system.
Yes indeed! If you read through the previous posts, you will see that this is the message we have been trying to convey!
 
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