Project Ideas : Questions stating an independent and a dependent variable about astronomy topics.
More Astronomy Science Project Ideas
Insolation : This link provides information about insolation only, but you could easily design an investigation in which you would mathematically compare insolation for solar-rays at different angle, and then design an investigation to experimentally measure the insolation. Percent error for the investigation could be calculated using the math calculations as the standard.
Inertia Used to Measure Mass : This information could be used to design a science project.
Scientific Method: Color Mixing : A brief overview of using color mixing for a science project.