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

The body of mass 25 kg is taken from the earth to the moon. If the value of g on moon is 1.6 ms^-2 then the weight of the body on moon is :

1. 50 N
2. 100 N
3. 40 N
4. 60 N

The S.I. unit of weight is :

1. kg
2. Joule
3. Newton
4. dyne

The mass of a body :

1. changes with a change of place
2. changes with direction
3. changes when the velocity of the body is close to the velocity of light
4. none of these