a ruler, a stopwatch, a tennis ball, a 1- meter long piece of string, a rubber band, tape and 10 pieces of paper. Only using this items I need to come up with an Experiment Pleaseee help.

Suppose that three astronomical objects, 1, 2, and 3 are observed to lie on a line, and the distance from object 1 to object 3 is d. object 1 has four times the mass of object 3, and seven times the mass of object 2. find the distance between objects 1 and 2 for which the net force on object 2 is zero.