Why a bullet shot on a tightly fitted window glass sheet makes a small circular hole, while a cricket ball damages a big portion of the same sheet ?
Answers
Obviously the size of the projectile plays a part. What is more important is the fact that the bullet applies its force at the point of impact which is the tip, and punches a hole through the glass by applying that great force in a very small area.
The cricket being much larger and slower moving does not punch its way through as much as it batters its way through. Instead of applying the force at a single instant relatively speaking the ball transfers more of its energy to the glass whereas the bullet only transfers a small portion of its energy to the glass.
The ball might also flatten out to a small degree making itself even larger as it penetrates.
You can think of it this way. The cricket ball is akin to an old lead .60 caliber Brown Bess musket ball and the modern bullet is itself. The lead musket ball hits something and begins to deform becoming larger in diameter perpendicular to its direction of impact. I creates a large hole and slows rapidly as it expands in the material it is penetrating. A modern bullet on the other hand is harder, and does not deform and keeps its shape. So it penetrates neatly and almost surgically through the material and exits the other side having retained most of the energy it had when it impacted the glass.
Ballistics experts grapple with this over penetration problem a lot when dealing with the ability to kill and incapacitate. A bullet like that can penetrate the human body and barring hitting something vital will not immediately incapacitate a person who can then retaliate and maybe even kill you. Not to mention the bullet is still going and may hit someone else and kill them too.
The problem to solve is how to keep the bullet INSIDE the target and transfer all those thousands of pounds of energy into the person to incapacitate them. So bullets of different designs have been invented with the expressed purpose of expanding rapidly upon impact to reduce penetration and to thereby transfer all the energy to the target.
I an not disparaging the ability of a cricket ball as a deadly projectile. I understand a crown prince Fredrick of England was killed by one in a cricket match.