Can weight=atmospheric pressure*mass

  • Thread starter masti6
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Main Question or Discussion Point

As w=force*mass..
but we can use atmospheric pressure instead of gravitational force because as per the law of gravity,the force exerted between the body are equal in magnitude. so the when atmospheric pressure is exerted on body the body will also exert same force to atmosphere
thus,
can w=atmospheric pressure*mass??
 

Answers and Replies

  • #2
Doc Al
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Newton's 3rd law tells us that the force exerted by the air on a body is equal and opposite to the force exerted by the body on the air. But this has nothing to do with the weight of the body, which is the gravitational force exerted by the earth on the body.

can w=atmospheric pressure*mass??
Note that the units do not match, so this equation is not physically meaningful.
 
  • #3
ZapperZ
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As w=force*mass..
but we can use atmospheric pressure instead of gravitational force because as per the law of gravity,the force exerted between the body are equal in magnitude. so the when atmospheric pressure is exerted on body the body will also exert same force to atmosphere
thus,
can w=atmospheric pressure*mass??
I often work in ultra-high vacuum chambers. If you are correct, stuff should start "floating" in those chambers because the atmospheric pressure is almost nil, causing it to have no weight.

Now do you think this actually happen?

Zz.
 
  • #4
tiny-tim
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welcome to pf!

hi masti6! welcome to pf! :smile:
… when atmospheric pressure is exerted on body the body will also exert same force to atmosphere
yes, the force of the body on the atmosphere is equal (and opposite) to the force of the atmosphere on the body

if you have a cube, the atmospheric pressure on the four sides will be equal to each other, and they will cannel out

however, the atmospheric pressure on the bottom will be slightly more than the atmospheric pressure on the top, by an amount density*height*g upward

so this will also be the net force exerted by the cube downward on the atmosphere (if there is atmosphere under the cube, and not something solid)
can w=atmospheric pressure*mass??
no, not unless the atmosphere is so thick that the body can float in it (eg on Jupiter)

if the cube is resting on the ground, the force on the ground will be the weight w (= mg) minus the "buoyancy" force density*height*g :wink:
 

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