Two objects attract each other gravitationally with a force of 2.9 10-10 N when they are 0.35 m apart. Their total mass is 4.0 kg. Find their individual masses.
F = GMm/r^2
if one mass is m, the other is 4.0-m, so
2.9*10^-10 = 6.67*10^-11 * m(4.0-m)/0.35^2
m = 3.86 or 0.14 kg