Question

a student designs a gravity experiment. she will time how long it takes different objects to fall from her schools roof to the ground. she will use three objects: a 2 - foot - long board, a toy car, and a paper bag. what is wrong with her experiments design? (1 point)
gravity will not affect how long it takes for the objects to fall to the ground.
the school roof is not tall enough to test the effect of gravity on different objects.
the objects do not have the same size, shape, or mass, so any differences in drop times cannot be attributed to one variable.
the experiment does not test enough objects.

Explanation:

In a scientific experiment, to determine the effect of a single variable (in this case, if we assume the intention was to test something related to gravity's effect on fall time - though gravity's effect on time of fall for free - fall in a vacuum is independent of mass, but with air resistance, shape, size, and mass matter), we need to control variables. Here, the objects (board, toy - car, paper - bag) have different sizes, shapes, and masses. So, when measuring fall time, differences cannot be clearly linked to one variable. Gravity does affect fall time (so the first option is wrong). There's no indication the school roof is too short (second option is baseless). The number of objects (three) is not the core issue; the variable control is.

Answer:

The objects do not have the same size, shape, or mass, so any differences in drop times cannot be attributed to one variable.