# Homework Help: Physical Pendulum

1. May 11, 2010

### bon

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

Ok worked out the time period of a physical pendulum (T) to be (in terms of constant a, and variable length x):

T^2 = 4pi (1/2a^2 + x^2)/(gx)

Now asked how i could use a measurement of T(x) to measure g.

2. Relevant equations

3. The attempt at a solution

I guess i have to vary x and measure T and plot some sort of graph, but given the relation above I can't see what the easiest way to determine g would be...

thanks

2. May 11, 2010

### rock.freak667

Normally, if you have to plot a graph to get 'g', you'd try as best as you could to make the equation into the form Y=MX+C.

Eg. T2=4π2(L/g), you write this as T2=(4π2/g)L

So that Y=T2 and X=L, plot Y vs. X.

3. May 11, 2010

### bon

Thanks but I knew this - I'm just not sure how to do this in this case..

4. May 11, 2010

### rock.freak667

$$T^2 = 4 \pi \frac{\frac{1}{2}a^2 + x^2}{(gx)}$$

$$T^2 =\frac{4 \pi}{g} \frac{\frac{1}{2}a^2 + x^2}{x}$$

5. May 11, 2010

### bon

Thanks but you still have the x at the bottom..

6. May 11, 2010

### rock.freak667

I meant X=((1/2)a2+x2)/x

7. May 11, 2010

### bon

Oh rite i see. Thanks