# Homework Help: Colombo's Law Gizmo

1. Nov 6, 2014

### garr6120

1. The problem statement, all variables and given/known data
Write the equation that you determined from your results that shows the relationship between F and d for two charged objects.

2. Relevant equations

3. The attempt at a solution
I have determined a constant value that relates force to seperation distance. The value is 8500 N/m^2
I'm assuming the equation is (8500 N/m^2)/r^2, where the 8500 N/m^2 is equal to the two charges and coloumb's constant multiplied together. and r is the distance between the two charges.

2. Nov 7, 2014

### andrevdh

Did you draw a F versus 1/d2 graph with your data?

3. Nov 7, 2014

### garr6120

First I drew F vs. 1/d graph which gave me a hyperbola and then my F vs. 1/d^2 graph gave me a linear line and i have calculated the slope of that linear line to be 8500 which has some percent error.

4. Nov 7, 2014

### andrevdh

Yes, that shows that the relationship between F and 1/d2 is
linear or that there is a directly proportional relationship if the y-intercept
is close to zero newton. The gradient is then the proportional constant,
which you determined as 8500. Have a careful look at its unit though.
The empirical equation (supply the units of your constant in the brackets)
is then
F = 8500 ( ) 1/d2 or r2

5. Nov 7, 2014

### garr6120

For it's units i get N/m^2 but when i actually multiply coulomb's constant and both q's together i get units of Nm^2 my slope should have the same units as the actual theoretical k.

6. Nov 7, 2014

### andrevdh

The units of the independent variable is per meter square. So the units of the gradient will be N/m-2 which comes to Nm2