Which physical quantity is represented by the ratio of momentum and velocity of the body?

Which one of the following statements about speed and velocity is correct?

Which one of the following is dimensionless quantity?

A car has an initial velocity of 12 m/s and is brought to rest over a distance of 45 m. The acceleration of the car is

The ratio of kinetic energies of two bodies of same mass is 4 : 9, the ratio of their velocities will be

What is the effect of pressure of a human body on sand ?