On an electron in an atom both electric and gravitational forces are collinear we neglect gravitational force (F_G) in comparision to electric force (F_E ), because

• F_E > F_G

• F_N > F_E

• F_E >> F_G

• F_N >> F_G

The gravitational field is given by E = − xi − 2y²j. When gravitational potential is zero at (0, 0), then the gravitational potential at (2, 1) is

• 3 unit

• 6 unit

• 9 unit

• 12 unit

A satellite orbiting the earth in a circular orbit of radius R completes one revolution in 3 h. If orbital radius of geostationarysatellite is 36,000 km, orbital radius of earth is 

• 6000 km

• 9000 km

• 12000 km

• 15000 km

Acceleration due to gravity is g on the surface of the earth. Then the value of the acceleration due to gravity at a height of 32 km above earth's surface is (Assume radius of earth to be 6400 km)

• 0.99 g

• 0.8 g

• 1.01 g

• 0.9 g

If the mass of moon is $\frac{1}{90}$ of earth's mass, its radius is $\frac{1}{3}$ of earth's radius and if g is acceleration due to gravity on earth, then the acceleration due to gravity on moon is

• $\frac{\mathrm{g}}{3}$

• $\frac{\mathrm{g}}{90}$

• $\frac{\mathrm{g}}{10}$

• $\frac{\mathrm{g}}{9}$

Which of the following statements about the gravitational constant is true ?

• It is a force

• It has no unit

• It has same value in all systems of units

• It does not depend on the nature of the medium in which the bodies are kept

Two identical solid copper spheres of radius R are placed in contact with each other. The gravitational attraction  between them is proportional to

• R²

• R^-2

• R⁴

• R^-4

A pellet of mass 1 g is moving with an angular velocity of 1 rad/s along a circle of radius 1 m the centrifugal force is

• 0.1 dyne

• 1 dyne

• 10 dyne

• 100 dyne

Two point objects of masses 1.5 g and 2.5 g respectively area at a distance of 16 cm apart, the centre of gravity is at a distance x from the object of mass 1.5 g where x is

• 10 cm

• 6 cm

• 13 cm

• 3 cm

130.

The weight of a body on surface of earth is 12.6 N. When it is raised to a height half the radius of earth its weight will be

• 2.8 N

• 5.6 N

• 12.5 N

• 25.2 N