What is Force?
Force is a push or a pull upon an object resulting from its interaction with another object. Let us understand the concept of force with the following examples:
Stationary ball
Consider a stationary ball. Even though we are not physically pushing or pulling a stationary ball, it is still experiencing force. It is the gravitational force acting on the ball in the downward direction.
Gravitational force and normal force example
 To balance this force, the ground applies an equal force on the ball in the upward direction. This force is known as Normal force or the normal reaction force, which is an outcome of the interaction between the ball and the ground. Since the forces are equal and opposite, they cancel out each other and the net force on the ball is zero.
From this, we can conclude that when forces are acting on a body, it does not imply that an object is in motion. A body continues to remain at rest if the net force on it is zero.
Pushing a stationary ball
Consider the above example of a stationary ball. If we apply a little push to this ball, the ball begins to move and its position changes.
This happens because there is another force acting on the ball, making the net force on the ball non-zero. This force is nothing but the little push applied on the ball.
But you will notice one more thing here – on pushing the ball, it starts moving but soon comes to a standstill. This is because there is another force acting on the moving ball. This is the frictional force between the ball and the ground, acting in a direction opposite to that of the motion of the ball. This force is the outcome of an interaction between a moving object and the surface it is in contact with.
Frictional force example
 Ball moving with uniform velocity on a frictionless ground
Consider a ball moving on a frictionless ground with a uniform velocity. The downward gravitational force is still balanced by the normal reaction force of the ground. And as there is no friction between the ground and the ball, the net force on the ball remains zero.
In such a case, the ball will continue to move endlessly with a uniform velocity. From this, we can conclude that an object will continue to move with a uniform velocity if the net force on it is zero.