A body falls downwards because of :

1. electrical force
2. gravitational force
3. mechanical force
4. magnetic force.

A force to be expressed correctly requires :

1. only the magnitude
2. only the direction
3. both the magnitude and direction
4. none of the above.

Friction :

1. promotes motion
2. opposes motion
3. acts in the direction of motion
4. is always a nuisance.

Friction is reduced by :

1. making the surfaces wet
2. making the surfaces dry
3. making the surfaces rough
4. sprinkling sand on the surface.