Determine Dimensions of Physical Quantities: F, p

[you_of_eh]

From the following defining equations, determine the dimensions of the names physical quantities. Use L to represent the dimension length (distance), T to represent time and M to represent mass.

a) force, F: F=ma, (where m is mass and a is acceleration)
b) pressure, p: p=F/A, (where F is a force (see previous question) and A is an area)

-I don't need the answer it's just that I can't even attempt to solve the question as I have no idea what the question is asking for.

a) F=M*d(L/T)/dT ?
b) p=M*d(L/T)/dT/L^2 ?

..that is all that I could come up with.

Thank you for your time.

 

[berkeman]

From the following defining equations, determine the dimensions of the names physical quantities. Use L to represent the dimension length (distance), T to represent time and M to represent mass.

a) force, F: F=ma, (where m is mass and a is acceleration)
b) pressure, p: p=F/A, (where F is a force (see previous question) and A is an area)

-I don't need the answer it's just that I can't even attempt to solve the question as I have no idea what the question is asking for.

a) F=M*d(L/T)/dT ?
b) p=M*d(L/T)/dT/L^2 ?

..that is all that I could come up with.

Thank you for your time.

Welcome to the PF. You are close... For a), just clean up what you have, and leave out the d symbols. The units of a change in length are still length. Does that help?

 

[you_of_eh]

OK yea I get it..

a) F = M(L^3)(T^2)
b) p = ML/T^2

 

[berkeman]

OK yea I get it..

a) F = M(L^3)(T^2)
b) p = ML/T^2

Much closer. But you messed up a division in a) (I didn't check b).

Hint -- The unit of force is a Newton. Look up what the sub-units are that make up a N.

 

[you_of_eh]

Well I checked it a couple times..seems correct to me.

 

[Zhalfirin88]

Try plugging in actual units. M = kg, L = m, T = s

For a) you're saying F = M(L^3)(T^2)

which means, N(Newton) = kg * m³ * s², and that is close, but not right.

Edit: Also, b) is wrong. Again, p = ML/T^2 is close, but not right.

You're saying, p = kg * m / s²