Astudent designs an experiment where he takes a small wood car with 1.0 inch diameter wheels and rolls it down a ramp. the student measures the speed of the car when it reaches the bottom of the ramp. the student then takes a small plastic car with 1.5 inch diameter wheels and repeats the process. finally, the student takes a small metal car with 2.0 inch diameter wheels and repeats the process a final time. the student notes that the metal car had the fastest speed at the bottom of the ramp. the student can conclude:

As the radius of a wheel , in rolling motion on a inclined plane, changes , its final speed , does not change . In other words , acceleration of wheel on inclined plane does not depend upon radius of the wheel . It also does not depend upon the mass of the wheel.

Explanation:

In case of perfect rolling on an inclined plane, the acceleration of body is given by the following expression.

a = g/1+k²/r² where k is known as radius of gyration . For a wheel its value is equal to( 1/√2)r.r is radius . From this expression , one can conclude that acceleration and therefore velocity does not depend upon radius of the wheel . Therefore the reason of the metal car having greatest speed  is the resistance of air and friction of surface being the least in its case.