written by D. J. Wagner and Samuel Harryman

As part of a larger investigation into students' conceptions about buoyancy, we investigated the prevalence
of the belief that the gravitational force on an object changes when the object is placed in a fluid. We also
investigated the effect of describing the force as "weight" instead of "gravitational force." During the first phase
of the study (Winter 2016 to Fall 2016), students at two different institutions were asked to identify the correct
free-body diagram (FBD) for a ball floating in water, and then for the same ball held down while fully
submerged under water. Half of the students were shown FBDs involving "weight," and the other half were
shown FBDs involving the "gravitational force." During the second phase of the study (Fall 2017 to Spring
2019), students at one of the institutions were asked to explicitly compare the strength of either the weight or
the gravitational force on the ball when it was falling, floating, and held submerged. This paper will report on
the fraction of students who indicated that the weight or gravitational force differed between the scenarios and
will discuss the effects of both the question asked and the wording used to describe the force.

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Last Modified December 31, 2019

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