When a cannon with a longer barrel is fired, the force of expanding gases acts on the cannonball for a longer distance. What effect does this have on the velocity of the emerging cannonball? (Do you see why long-range cannons have such long barrels?)

what effect can it possibly have?

increase
decrease
unaffected

The very language of the question gives away the answer.

When a cannon with a longer barrel is fired, the force of expanding gases acts on the cannonball for a longer duration. This has a direct impact on the velocity of the emerging cannonball. To understand why long-range cannons have such long barrels, we need to explore the principles of physics involved.

The force acting on a cannonball comes from the rapid expansion of gases produced by the combustion of gunpowder inside the cannon's chamber. This force propels the cannonball forward, causing it to gain velocity. In a shorter barrel, the expanding gases have less time to act on the cannonball before it leaves the barrel. As a result, the cannonball does not achieve its maximum velocity.

However, in a cannon with a longer barrel, the expanding gases continue to exert force on the cannonball for a longer distance. This prolonged interaction allows the cannonball to experience a more substantial acceleration and gain a higher velocity as it leaves the barrel. The longer the barrel, the longer the force of expanding gases can act on the cannonball, resulting in a greater final velocity.

In summary, by increasing the barrel length, long-range cannons enable the expanding gases to act on the cannonball for a longer duration, leading to a higher velocity. This is why long-range cannons have such long barrels - to maximize the projectile's velocity and achieve greater range.