Two metals spheres of the same material and of equal radius R are touching each other.Prove that the force of attraction between them is proportional to R^4

A planet is rotating round a heavy star along a circular path of radius R with time T. if the gravitational force of attraction between planet and star is proportional to R^(-5/2) , then T^2 prop R^x . What is the value of x ?

A planet is rotating round a heavy star along a circular path of radius R with time T. If the gravitational force of attraction between planet & star is proportional R^(-5//2) then T^2 prop R^x what is the value of x?

Two lead spheres are kept at a distance of 30 cm . The mass of each sphere is 100 kg. The mutual force of gravitational attraction between them is equal to the weight of a mass of 0.75 mg. Determine the gravitational constant .

The ratio of the lengths of two wires made of the same metal and of equal radius is 1:2 IF both the wires are stretched by the same force, then the ratio of the strains will be

Two insulated metal spheres of the same size are charged with -15 esu and +25 esu. The distance between their centres is 10 cm. What is the force acting between the two charges? If the two spheres are made to touch each other and then placed in their previous positions, what will be the force acting between them?

Two wires made of same material have equal length and radius of one of them is twice that of the other. Find the ratio of their resistances.

Two spheres of the same material have the same radius but one is hollow while the other is solid. Both spheres are heated to same temperature. Then

Find the number of sphere of radius r touching the coordinate axes.