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Pressure of falling sand

  • Thread starter JSmith123
  • Start date
  • #1
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Homework Statement


Grains of sand of mass 3.10 10-3 g each, fall from a height of 0.8 m on a sticky surface at a rate of 50 grains per second per cm^2. What pressure does this shower of sand exert on the surface, assuming that air resistance can be neglected?


Homework Equations


P=F/A
F=ma=mv d/dt


The Attempt at a Solution


So I understand I have to calculate the velocity and multiply that by the mass and number of grains. What I don't understand is the area. What is the area? Any help would be great.
 

Answers and Replies

  • #2
1,137
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use F = dP/dt to find force due to 1 grain ..... multiply with total number of grains ..... and then divide the area on which this total force is acting .... you get pressure
 
  • #3
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use F = dP/dt to find force due to 1 grain ..... multiply with total number of grains ..... and then divide the area on which this total force is acting .... you get pressure
I see, but what is the area?
 
  • #4
1,137
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from P = F/A you can see that P=F when area is 1m^2

and you can also find force in 1cm^2

so its easy to find force in 1m^2 also, right?
 
  • #5
4
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Oh jeez the area is just 1m^2? I can't believe I didn't notice that. Anyways, thanks for the help.
 

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