When trying to turn a key into a lock, following is applied

The weight of a body is due to

A. Centripetal force of earth

B. Gravitational pull exerted by the earth

C. Force of attraction experienced by par-ticles

D. Gravitational force of attraction towards the centre of the earth

The product of either force of couple with the arm of the couple is called

A. Resultant couple

B. Moment of the forces

C. Resulting couple

D. Moment of the couple

A sample of metal weighs 219 gms in air, 180 gms in water, 120 gms in an unknown fluid. Then which is correct statement about density of metal

A. Density of metal can’t be determined

B. Metal is twice as dense as water

C. Metal will float in water

D. Metal is twice as dense as unknown fluid

Coulomb friction is the friction between

A. Bodies having relative motion

B. Two dry surfaces

C. Two lubricated surfaces

D. Solids and liquids