Three point masses are placed on the -axis at fixed positions in empty space: at
PHYSICS · Subjective · A Level · Physics · Fields and their consequences · Fields and their consequences
Problem
Three point masses are placed on the x-axis at fixed positions in empty space: m1=5kg at x=0, m2=10kg at x=0.50m, and m3=20kg at x=1.20m.
(a) Write a general expression for the net gravitational field strength E(x) on the x-axis due to all three masses.
(b) By setting E(x)=0, obtain the polynomial equation whose roots correspond to positions of zero field strength.
(c) Show that there are exactly two physically meaningful roots and determine their numerical values correct to two significant figures.
(d) Indicate which of the two roots lies between two of the given masses and provide a physical explanation for why a null point cannot exist between the remaining pair.