This experiment measures the acceleration of gravity g from the range of a projectile. You fire a ball at a fixed speed and a range of angles, reading the landing distance off a tape each time. Theory says the range is linear in sin(2θ), and the slope of that line gives you g.
What makes this one different
In Hooke’s spring you learned that the intercept of a linear fit exposes the zero-point error of your instrument. The same trick works here: the tape you measure the range with has an offset, and it shows up in the intercept.
But this experiment carries a harder lesson too. When you compute g, you will almost certainly get a value that is too large — and by more than your own ± allows. The cause is air drag: it shortens every shot in the same direction, so it never appears as scatter and your error bar cannot see it. That is the difference between random and systematic error: more shots shrink the first and do nothing at all to the second.