Two separate experiments are performed to measure gravitational attraction

PHYSICS · Multi-part · A Level · Physics · Fields and their consequences · Fields and their consequences

Problem

Two separate experiments are performed to measure gravitational attraction. • Experiment A uses masses

4\,\text{kg}

and

6\,\text{kg}

and produces a straight-line graph with slope

S_A = 2.00\times10^{-10}\,\text{N\,m}^{2}

when

F

is plotted against

\dfrac{1}{r^{2}}

. • Experiment B uses one mass of

4\,\text{kg}

and another mass

M

(unknown). The corresponding graph has slope

S_B = 3.00\times10^{-10}\,\text{N\,m}^{2}

. (i) Show that the ratio

\dfrac{S_B}{S_A}

equals

\dfrac{M}{6\,\text{kg}}

. (ii) Hence find the value of the unknown mass

M

. (iii) Explain why both experiments give graphs of identical shape even though their slopes differ.