Why doesn't a new ball-point pen write as smoothly as one being written for a little? You will say that the friction is more first up.Then why is that so?
Friction is higher at the beginning. Usually, a ballpoint pen comes with a tip to protect the ink inside. This causes the ink at the surface to harden after a while, hence, producing more friction. However, upon writing, this hardened layer slowly goes away, and liquid ink begins to flow out, producing less friction.
A ballpoint pen consists of an extremely hard ball (tool steel or tungsten carbide) seated in a soft metal shank tip (usually brass). This will form a low-friction bearing but to do so, some initial wear between them is required for the ball to "seat" properly in the shank. In the process of seating in, tiny asperities on the surface of the shank and the ball get embedded into the surface of the shank, which gradually reduces the amount of friction created as the ball rolls in the shank. Most ballpoint manufacturers strive to seat in the balls by writing with the pens in a machine briefly before packaging them. But if that process did not go to completion on the machine, then it will occur when you begin writing with the pen.
Friction is the only answer. It be expressed clearly as below. We cannot write on water, because force exerted by water is less than weight of ink. We can write on paper by because normal force is very high than weight of ink inside. Intially,weight of ink is more so we need to apply more force. Obviously frictional force increase as it is proportional to normal force. Due continuous use The ball becomes less rough. As it used a lot the gap between ball and pen increases, creating a smooth flow of ink. All the reasons are responsible for smooth flow.