Imagine a light planet revolving around a very massive star in a circular orbit of radius r with a period of revolution T. On what power of r, will the square of time period depend if the gravitational force of attraction between the planet and the star is proportional to 


Correct option is


As gravitation provides centripetal force




Two equal masses m and m are hung from a balance whose scale pans differ in vertical height by h. Calculate the error in weighing, if any, in terms of density of earth ρ.


Three particles each of mass m are placed at the corners of an equilateral triangle of side d. Calculate (a) the potential energy of the system, (b) work done on this system if the side of the triangle is changed from d to 2d.


What will be the acceleration due to gravity on the surface of the moon if its radius were (1/4)th the radius of earth and its mass (1/80)th the mass of earth? What will be the escape velocity on the surface of moon if it is 11.2 km/s on the surface of the earth? (Given that g = 9.8 m/s2)


The masses and radii of the earth and moon are M1R1 and M2R2respectively. Their centres are at distance d apart. What is the minimum speed with which a particle of mass m should be projected from a point midway between the two centres so as to escape to infinity?


Distance between the centres of two stars is 10a. The masses of these stars are M and 16M and their radii a and 2a, respectively. A body of mass m is fired straight from the surface of the larger star towards the smaller star. What should be its minimum initial speed to reach the surface of the smaller star? Obtain the expression in terms of GM and a.


A mass  (= mass of earth) is to be compressed in a sphere in such a way that the escape velocity from its surface is 3 × 108 m/s (equal to that of light). What should be the radius of the sphere?


A projectile is fired vertically upward from the surface of earth with a velocity Kve where ve is the escape velocity and K < 1. Neglecting air resistance, show that the maximum height to which it will rise measured from the centre of earth is R/(1 – K2) where R is the radius of the earth.


A particle is fired vertically upwards from the surface of earth and reaches a height 6400 km. find the initial velocity of the particle if R = 6400 km andg at the surface of earth is 10 m/s2.


Calculate the mass of the sun if the mean radius of the earth’s orbit is 


Halley’s comet has a period of 76 years and in 1986, had a distance of closest approach to the sun equal to  What is the comet’s farthest distance from the sun if the mass of sun is  units?