# Homework Help: Dimensionally corect equation ?

1. Sep 10, 2008

### star20

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

-------------Dimension------------------...
distance (x) (L) Acceleration (a) (L)/(T)^2

Time (t)-----> (T) Force (F)-----> (M)(L)/(T)^2

Mass (m)----> (M) Energy (E)-----> (M)(L)^2/(T)^2

Speed (v)-----> (L)/(T)
Is the following equation dimensionally correct?
A) X= 1/2 at^3

2. Relevant equations

3. The attempt at a solution

A) X= 1/2 at^3
[L] = 1/2 [L]/[T]^2 * [T]^3

i know my proff said numbers such as 1/2 don't have dimension but i dont really understand how to solve this....what am i suppsoed 2 do with 1/2

2. Sep 10, 2008

### Hootenanny

Staff Emeritus
Welcome to PF Star20,

QUOTE=star20;1867892]

A) X= 1/2 at^3
[L] = 1/2 [L]/[T]^2 * [T]^3

i know my proff said numbers such as 1/2 don't have dimension but i dont really understand how to solve this....what am i suppsoed 2 do with 1/2[/QUOTE]
Scalar coefficients are irrelevant in dimensional analysis, only the dimensions themselves are important, you can safely ignore the fact of 1/2.

3. Sep 10, 2008

### Dick

Drop the (1/2). It doesn't have any dimensions.

4. Sep 10, 2008

ok thanks