# F vs. a Graph's Intercept

1. Oct 7, 2006

### Soaring Crane

My question concerns the y-intercept of the force vs. acceleration graph. When I plotted my data, the regression line had an intercept that was not 0. What does this signify? I know that the intercept is the amount of force when the acceleration is 0 m/s^2. Shouldn't it be 0 N at 0 m/s^2? Does this mean there was a source of force that I neglected to take account for while recording the values for the graph?

Thanks.

2. Oct 7, 2006

### arildno

Most likely!
Force is strictly proportional to acceleration.

3. Oct 7, 2006

### Integral

Staff Emeritus
Just how non-zero is it? Could it be an indication of measurement errors?

4. Oct 8, 2006

### andrevdh

Consider the case if the graph was drawn a vs F.

The x-intercept will indicate that some non-zero force was necessary to start the acceleration of the object - a tipical real life situation we find in order to overcome the ever present frictional forces.

5. Oct 8, 2006

### Soaring Crane

The intercept was about 0.0051 (N).

6. Oct 8, 2006

### arildno

What are the typical magnitude of your data values?

7. Oct 8, 2006

### Soaring Crane

Which values? The a values or the F values?

All the force and acceleration values are less than 1.0 N and 1.0 m/s^2, respectively.

My smallest F value is 0.0961 N and greatest is 0.446 N.

My smallest a value is 0.188 m/s^2 and greatest is 0.869 m/s^2. The smallest F value corresponds with my smallest a value, and the greatest F value corresponds with my greatest a value.

8. Oct 8, 2006

### Soaring Crane

A frictionless setup was organized (or was attempted to be organized), but it is possible to still have frictional forces as a source of error?

9. Oct 8, 2006

### arildno

Indeed there can, and will be!
In your case, the force discrepancy is about a twentieth of your least value, that is most likely the effect of friction showing up.