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Normal Force

  • Thread starter lacar213
  • Start date
  • #1
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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
 

Answers and Replies

  • #2
Doc Al
Mentor
44,877
1,129

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.
 
  • #3
29
0
So the 170 needs to be negative .. ?
Fn + (-170) - 372.4 = 0
Fn = 542.4
 
  • #4
Doc Al
Mentor
44,877
1,129
Looks good!
 

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