What is the magnitude of the normal force in this block stacking scenario?

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Homework Help Overview

The problem involves three blocks stacked on a frictionless surface, with a downward force applied to the top block. The objective is to determine the normal force exerted by the bottom block on the middle block.

Discussion Character

  • Exploratory, Assumption checking

Approaches and Questions Raised

  • Participants discuss the forces acting on the blocks, including the applied downward force and gravitational forces. There is an attempt to set up an equation to solve for the normal force, with some questioning the sign of the applied force.

Discussion Status

Participants are actively engaging with the problem, with one confirming a calculation and another questioning the treatment of the downward force. There is no explicit consensus on the final value of the normal force yet, but the discussion is progressing with corrections and confirmations of reasoning.

Contextual Notes

Participants are navigating through the implications of the applied force and gravitational forces, with attention to the direction of these forces in their calculations.

lacar213
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Homework Statement


Three blocks are arranged in a stack on a frictionless horizontal surface. The bottom block has a mass of 37.0 kg. A block of mass 18.0 kg sits on top of it and a 20.0 kg block sits on top of the middle block. A downward vertical force of 170 N is applied to the top block. What is the magnitude of the normal force exerted by the bottom block on the middle block?



Homework Equations


Fn + T + (-mg) = 0


The Attempt at a Solution


20 + 18 = 38*9.8 = 372.4 N
Fn + 170 - 372.4 = 0
Fn = 202.4
 
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lacar213 said:

The Attempt at a Solution


20 + 18 = 38*9.8 = 372.4 N
Good.
Fn + 170 - 372.4 = 0
Careful: That 170 N force acts downward.
 
So the 170 needs to be negative .. ?
Fn + (-170) - 372.4 = 0
Fn = 542.4
 
Looks good!
 

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