Calculating Pressure from Falling Sand Shower

  • Thread starter Thread starter JSmith123
  • Start date Start date
  • Tags Tags
    Falling Pressure
AI Thread Summary
To calculate the pressure exerted by falling sand grains on a surface, the mass of each grain is 3.10 x 10^-3 g, and they fall from a height of 0.8 m at a rate of 50 grains per second per cm². The pressure can be determined using the formula P = F/A, where F is the total force and A is the area. The force can be calculated by finding the velocity of the grains and multiplying it by the mass and total number of grains. Clarification was provided that the area can be considered as 1 m² for ease of calculation. Understanding the area is crucial for accurately determining the pressure exerted by the sand shower.
JSmith123
Messages
4
Reaction score
0

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.
 
Physics news on Phys.org
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
 
cupid.callin said:
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?
 
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?
 
Oh jeez the area is just 1m^2? I can't believe I didn't notice that. Anyways, thanks for the help.
 
Thread 'Variable mass system : water sprayed into a moving container'
Starting with the mass considerations #m(t)# is mass of water #M_{c}# mass of container and #M(t)# mass of total system $$M(t) = M_{C} + m(t)$$ $$\Rightarrow \frac{dM(t)}{dt} = \frac{dm(t)}{dt}$$ $$P_i = Mv + u \, dm$$ $$P_f = (M + dm)(v + dv)$$ $$\Delta P = M \, dv + (v - u) \, dm$$ $$F = \frac{dP}{dt} = M \frac{dv}{dt} + (v - u) \frac{dm}{dt}$$ $$F = u \frac{dm}{dt} = \rho A u^2$$ from conservation of momentum , the cannon recoils with the same force which it applies. $$\quad \frac{dm}{dt}...
I was thinking using 2 purple mattress samples, and taping them together, I do want other ideas though, the main guidelines are; Must have a volume LESS than 1600 cubic centimeters, and CAN'T exceed 25 cm in ANY direction. Must be LESS than 1 kg. NO parachutes. NO glue or Tape can touch the egg. MUST be able to take egg out in less than 1 minute. Grade A large eggs will be used.
Back
Top