Comparing Horizontal Forces on Stacked Blocks with Friction

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SUMMARY

The discussion centers on the dynamics of two stacked blocks under the influence of an external horizontal force. A 3kg block rests on a 2kg block, with a static friction coefficient of μs=0.3 between them. The conclusion drawn is that the total force acting on the top block (Ft) is greater than the total force acting on the bottom block (Fb), due to the necessity of overcoming friction to maintain the top block's motion. This is confirmed by the relationship between the forces acting on both blocks as they accelerate together.

PREREQUISITES
  • Understanding of Newton's Second Law (F=ma)
  • Knowledge of static friction and its coefficient (μs)
  • Concept of net forces in horizontal and vertical directions
  • Basic principles of block dynamics and acceleration
NEXT STEPS
  • Study the implications of static friction in multi-body systems
  • Learn about the effects of external forces on stacked objects
  • Explore Newton's laws of motion in greater detail
  • Investigate real-world applications of friction in engineering scenarios
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This discussion is beneficial for physics students, educators, and anyone interested in understanding the mechanics of forces acting on stacked objects, particularly in the context of friction and acceleration.

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Homework Statement


A block of mass 3kg sits on top of a block of mass 2kg. The static coefficient of friction between the blocks is μs=0.3, and this friction keeps the top block from sliding on the bottom block. There is no friction between the bottom block and the floor. A horizontal external force Fext is applied to the bottom block, causing the blocks to accelerate to the right.

How does the magnitude of the total force acting on the bottom block, Fb, compare to the magnitude of the total foce acting on the top block, Ft?

a. Ft>Fb
b.Ft=Fb
c.Ft<Fb


Homework Equations



None given but μs*N=Ffric and F=ma.

The Attempt at a Solution


I know that all of the forces in the y direction cancel but I am not sure how to tell which force is greater? I know that the answer is A but I am having trouble explaining it or showing work.
 
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In the y direction there is no acceleration of either block, thus, there is no net total force on either block in that direction. You should focus instead on the horizontal forces acting on each block. Since they both accelerate together at the same rate, which block must have the greater net total force acting on it in the horizontal direction, and why?
 

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