#1
I've taken Physics for A-Level, and I need abit of help with Homogeneous Equations, I understand that, if the left side of the equation equals the right it is homogeneous, but im finding it difficult to work them out.

Theres this one question that I was told to work out and I was just wondering if any of you could help me work it out.

The drag force "F", on a moving vehicle depends on its cross-sectional area A, Its velocity V and the density of the air ρ.
What are the SI Units for each of these four quantities?
By checking for homogeneity, work out which of these equations correctly links the variables:
A) F=A(to the power of two)ρV
B) F=Aρ(to the power of two)V
C) F=AρV(to the power of two)

Im not asking you to answer the question, im just wondering how I could get around this technique of working out these sort of questions.

Thanks, I will be grateful for any help.
#2
area => m^2
velocity => m/s
density of air => kg/m^3
force => kg*m/s^2


just put it the units into the equations and the one that doesn't amount to any fallacies is the right one
#5
HELP! i need somebody HELP!

Edit: fuuuuu!^^
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#6
Quote by Tokenmatt
I've taken Physics for A-Level, and I need abit of help with Homogeneous Equations, I understand that, if the left side of the equation equals the right it is homogeneous, but im finding it difficult to work them out.

Theres this one question that I was told to work out and I was just wondering if any of you could help me work it out.

The drag force "F", on a moving vehicle depends on its cross-sectional area A, Its velocity V and the density of the air ρ.
What are the SI Units for each of these four quantities?
By checking for homogeneity, work out which of these equations correctly links the variables:
A) F=A(to the power of two)ρV
B) F=Aρ(to the power of two)V
C) F=AρV(to the power of two)

Im not asking you to answer the question, im just wondering how I could get around this technique of working out these sort of questions.

Thanks, I will be grateful for any help.



hmmm naughty boy
#9
Neeeeeeeeeeeeeerds
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#10
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I Need Somebody

Not Just Anybody

Edit: Caps fail


My first thought was to write this.
#11
"When I was younger so much younger than todaaaaay"

On topic, the SI units for force, F, are Newtons, N. 1N=1kg*m/s^2.
Area, A, is m^2.
Density, rho (that p looking thing), is kg/m^3
V, velocity is m/s.

So, then try to get multiply the units on the right side to equal the units on the left.
you have 1/s^2 on the left, and the only one on the right with s is V, which needs to be squared to get m^2/s^2.

Then if that doesn't give it away, go to balance the kg. You have kg on the left, so you need rho on the right. So now you have F=rho*V^2*_. Notice that your units don't match yet.

Then balance the m, you have m on the left and 1/m on the right. You must multiply by m^2 (which are the units of A) to get m. Now you are balanced and have F=A*rho*V^2.

Hope I helped!
Stop whining and learn your theory!

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#12
I did physics at degree level, and I still aint helping you.. Altho I did drop out, and that was 5 years ago :S
@dbostwick