In introductory physics laboratories, a typical cavendish balance for measuring the gravitational constant g uses lead spheres of masses 1.56 kg and 21.1 g whose centers are separated by 5.34 cm. calculate the gravitational force between these spheres, treating each as a point mass located at the center of the sphere. the value of the universal gravitational constant is 6.67259 × 10−11 n · m2 /kg2 .