
#1
Mar2408, 01:30 PM

P: 13

1. The problem statement, all variables and given/known data
#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. Relevant equations Earth Atmoshpere pressure= ? P=Force(Newtons)/Area(m2) 3. The attempt at a solution 



#2
Mar2408, 01:35 PM

Emeritus
Sci Advisor
PF Gold
P: 5,198

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)? 



#3
Mar2408, 01:46 PM

P: 13

well how many newtons is one Earth Atmosphere pressure
I know ten newtons = 1kg arghhhhhhhhh 



#4
Mar2408, 01:58 PM

Emeritus
Sci Advisor
PF Gold
P: 5,198

Earth Atmosphere pressureAs 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=...UTF8&oe=UTF8 http://en.wikipedia.org/wiki/Atmospheric_pressure 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. 



#5
Mar2408, 02:01 PM

P: 13

thanks cepheid I kinda get it now




#6
Mar2408, 02:04 PM

Emeritus
Sci Advisor
PF Gold
P: 5,198

Alright...so what do you have to ask the person (in the problem) in order to solve it?




#7
Mar2408, 02:15 PM

P: 13

the area of their foot




#8
Mar2408, 02:18 PM

Emeritus
Sci Advisor
PF Gold
P: 5,198

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?




#9
Mar2408, 02:20 PM

P: 13

you need to know A = F/P




#10
Mar2408, 02:23 PM

P: 13

no wait F=A/P




#11
Mar2408, 02:24 PM

Emeritus
Sci Advisor
PF Gold
P: 5,198

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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