Question

why are the wheels og vehicle provided with mud guards

Answer 1

The mud particles stick to the wheel when they are wet. But, as the force of adhesion which causes the mud to stick to the wheel is not strong enough to provide centripetal force required to keep the mud stuck to the wheels. So, due to inertia of motion, the mud flies off in a direction tangential to the motion of the wheel.

This mud can fall on the rest of the vehicle body, the people standing nearby or the driver of the vehicle itself. A mud guard stops the flying mud and thus keeps everyone clean and safe.