Homework Help: Units and Dimensions

1. May 10, 2012

physics kiddy

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

Assuming that Pressure (P) of a particle is given by

P = b - t^2 / ax

where t = time, x = position
Find the dimension of b/a.

2. Relevant equations

3. The attempt at a solution

Using dimensional homogenity, I know that b represents time interval.

2. May 10, 2012

Infinitum

Is this (b-t2)/ax or b - (t2/ax)?

If it is the first, there is a subtraction of two quantities. Subtraction of what two quantities gives pressure? What does that tell you about b? and (t2/ax)?

If it's the second, what should be the dimension of b so that (t2/ax) can be subtracted from it? (apples and oranges? or, apples and apples? )

3. May 10, 2012

Staff: Mentor

Assuming you have represented the formula correctly .....
I don't think so. ...

your equation shows P comprising the sum of two components: b and (- t^2 / ax). Those two components must have identical units otherwise you couldn't add them, and what's more, they must have the same units as P.