Homework Help: Feel of physical quantities - help

1. Jul 18, 2009

1. The problem statement, all variables and given/known data

how can i have a feel of pressure ... i mean how much is 1 psi and how much is 10 psi pressure ..... can you plz give an example !

2. Relevant equations

i think pressure = force / area but still i dont undersatnd how much is 1 newton ... i mean i dont get a feel of it ...!

3. The attempt at a solution

lets say im 65 Kg and i do standard dips or say pullups then the kind of force i feel in my hands is = 65 kg* 9.8 N/kg / 2 = 325 N now how much pressure will lift me say my hands are 15 cm by 5 cm then its like 0.000075 m square then f/ Area pressure is like huge ...??
still dont get feel
any exam[ples of psi etc

2. Jul 18, 2009

tiny-tim

Welcome to PF!

Experiment:

Apparatus:

One girlfriend. One shoe (ordinary heel). One shoe (high heel, with reduced area). One sonic painometer.

Method:

i] get your girlfriend to stand on your foot in an ordinary heel.

ii] get your girlfriend to stand on your foot in a high heel.

Measurement:

Using the sonic painometer, record the level of sound produced.

This is caused by the difference in pressure.

3. Jul 18, 2009

RoyalCat

Re: Welcome to PF!

For analytic-quality results, you could replace the foot with the crotch.

In all seriousness though, one Newton is roughly 0.1 kgf, if you were to hold a 100 gram object in the palm of your hand, you'd feel it exerting around 1 Newton of force.

This table is pretty useful for getting your head around the different units for pressure:
http://en.wikipedia.org/wiki/Pascal_(pressure [Broken])
I recommend you compare things to atmospheric pressure, which is the pressure with which the air above you and around you is pressing down on you.

Last edited by a moderator: May 4, 2017
4. Jul 18, 2009

Redbelly98

Staff Emeritus
• 1 psi is the pressure increase when you are 2 feet underwater. Not huge, but noticeable.
• 10 psi is when you are 20 feet underwater.
• 100-200 psi is when somebody steps on your foot, with all their weight on their heel. Between uncomfortable and painful.

• 1 Newton is about the same as a 3 or 4 ounce weight. It is not much force, by everyday human standards.
• Most (adult) people weigh between 500 and 1000 Newtons.
Hope that helps.

5. Jul 18, 2009

Pengwuino

Wow those are some hilarious responses. I have a good one though

A typical psychotic physics teacher's example of the difference between pressure and force is the bed of nails. I think you can imagine the pain one would feel if you just let your body lay down on 3 nails or 1 nail. That's a force over a small area = high pressure = high pain. Now, if you constructed a bed of nails with hundreds of nails built in and were to lay down on it, you wouldn't feel much, let alone be sent to the hospital! That is an example of that same force over a much bigger area = lower pressure = lower insurance premiums. Don't try this at home but you can surely imagine the differences in pressure I hope. Remember, your body is always applying your weight on whatever is holding you up, no matter how spread out that force is applied.

6. Jul 19, 2009

wow soo many responses

i got it the feel of Psi, N , and this forum also, how people respond !!

i will stick here !

7. Jul 19, 2009