Question

In real life, objects never travel with uniform velocity even if it is a horizontal surface, something has to be done to them, why is it so? What is that something?

Answer 1

Hint: The acceleration of a body is responsible for changing its velocity. The presence of acceleration proves the existence of force. The body must be experiencing force if it has some acceleration.

Complete solution:
A body is said to have a uniform velocity if the net acceleration of the body is zero. The acceleration of a body is responsible for changing the velocity of the body. The velocity of the body will not change if there is no acceleration of the body. If we go a little deep then it means that if no force is acting on a body or all forces acting are balanced i.e. net force is zero, then the body will have no acceleration at all and so will move with a uniform velocity.
The figure alongside is the velocity-time graph of a body moving with a uniform velocity of 200cm/sec. Here, the slope of the graph also known as acceleration is zero throughout.

The next graph is the displacement-time graph for a body. It shows how the displacement varies with time for bodies having uniform velocities. The slope of this line is constant and does not change with time. This constant slope of the displacement-time graph is called velocity.

However, in real life nothing can move with uniform velocity. The uniform velocity is an ideal concept and is not possible, not even for horizontal surfaces. This is because; the forces acting on a body are never completely balanced. There are always unbalanced forces that result in some net acceleration. Presence of such unbalanced forces is the reason for non-zero net acceleration.
In real life nobody is completely free from forces, there always are some external forces acting on the body, forces like gravitational force, frictional force, etc. these create some resultant acceleration of the body. Hence, in real life objects cannot move with uniform velocity.
Even if there is a horizontal smooth surface the gravitational force cannot be neglected. Also, friction is something that is present in all surfaces. The zero friction surfaces are an ideal case so no such surface exists in real life. Hence even on a horizontal surface it is impossible for a body top move with uniform velocity.

Note:
(1) Friction should never be neglected when considering the forces acting on a body.
(2) The only case where friction can be zero is the ideal zero friction surface or if the body is not in contact with anything.
(3) Gravitational force always acts on all bodies on the surface of the earth.