The gravitational force between two masses is :

1. directly proportional to the product of the masses
2. inversely proportional to the square of the separation between them
3. significant between heavenly bodies, but is insignificant between atomic bodies.
4. all of the above

The gravitational force of attraction between two bodies of masses 60 kg and 40 kg separated by a distance 10 m is : (where G = 6.7 x 10^-11 Nm²kg^-2 )

1. 1.60 x 10^-9 N
2. 2.8 x 10^-11 N
3. 1.0 x 10^-11 N
4. 1.6 x 10^-11 N

A body is projected vertically upward with an initial velocity u. If acceleration due to gravity is g, the time for which it remains in air, is —

1. u/g
2. ug
3. 2u/g
4. u/2g

An object falling freely from rest reaches ground in 2 s. If acceleration due to gravity is 9.8 m s^-2 , the velocity of the object on reaching the ground will be —

1. 9.8 m s^-1
2. 4.9 m s^-1
3. 19.6 m s^-1
4. Zero