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Earth Atmosphere pressure

  • Thread starter mr.toronto
  • Start date
13
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1. Homework Statement
#1. What would have to be the area of a person's foot in order to impact a one Earth Atmosphere pressure? What do you need to ask?



2. Homework Equations
Earth Atmoshpere pressure= ?

P=Force(Newtons)/Area(m2)

3. The Attempt at a Solution
 

Answers and Replies

cepheid
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Okay, so you know that (solving your equation for area) that A = F/P.

You know P.
A is what you are trying to find out.

You DON'T know F.

So what do you have to ask (the person)?
 
13
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well how many newtons is one Earth Atmosphere pressure

I know ten newtons = 1kg arghhhhhhhhh
 
cepheid
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well how many newtons is one Earth Atmosphere pressure
First of all, pressure isn't measured in newtons. Pressure is force PER UNIT AREA. Force is measured in newtons, therefore pressure is measured in newtons per square metre (also known as pascals).

As for your question...come on! Seriously?!? You don't know what the typical atmospheric pressure is? Don't you ever watch the weather channel? Heh...I'm kind of joking around with you a bit, but even if you DON'T know it off the top of your head, it's something easily looked up. Here are two examples of how you could have saved me some time:

http://www.google.com/search?client=safari&rls=en&q=1+atmosphere+in+pascals&ie=UTF-8&oe=UTF-8

http://en.wikipedia.org/wiki/Atmospheric_pressure

I know ten newtons = 1kg arghhhhhhhhh
I'm afraid that this is nonsense. It doesn't make any more sense than saying that

3 metres = 2 seconds.

Just as length and time are two different physical quantities (meaning you can't equate them in any meaningful way), so too are force and mass.

A mass of 1 kg WEIGHS 10 newtons (and that's only true on Earth). That statement means that Earth will exert a gravitational FORCE of 10 newtons on a MASS of 1 kilogram.
 
13
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thanks cepheid I kinda get it now
 
cepheid
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Alright...so what do you have to ask the person (in the problem) in order to solve it?
 
13
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the area of their foot
 
cepheid
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Nope, not quite. The area of their foot is what you are trying to calculate (this is a hypothetical person whose foot exerts a pressure equal to atmospheric pressure). So, what information do you need to calculate that area? Well, you need P, and you need F. You know P (it has been given). You DON'T know F. So, what do you need to find out?
 
13
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you need to know A = F/P
 
13
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no wait F=A/P
 
cepheid
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you need to know A = F/P
Right, so to calculate A, you need BOTH F and P. But right now, you have only P. When the question says, "What do you need to ask?", it is asking you what additional information you need to solve this problem. Since you need both F and P, but you have only P, the additional information that you need is F. You can't solve the problem until you have F.

Now, what is F? How could you find it out (again, hypothetically)?

Note: this is a simple problem. They just have deliberately NOT given you all of the information you need to solve it. By asking you what additional information is required, they are just checking to see if you understand what the problem is asking.
 

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