Saturday, December 11, 2010


The third class assignment we completed was building a cannon.

This is what we built, kind of. Except that we made it out of popcans.
Cannons are capable of creating a lot of destruction by shooting out cannon balls or simply investing more energy into making much noise. Either way, a real cannon might seem intimidating, which is probably why many ancient battle tactics involved cannons. They had a wide variety of purposes, some of the most common ones involving sinking enemies ships or conquering strongholds.
By analyzing the reason why cannons were so popular we must look at the the way they achieve theirr parabolic motion. Cannons make use of projectile motion. Cannons make use of parabolic motion (due to a vertically shot cannon ball which is brought down by gravity.) Cannons also display the transformation of chemical potential energy into sound energy, kinetic energy, heat energy and work done.

In Kinematics we learned a formula that calculates the range of a projectile.
The velocity in the x-axis is constant because of negligible air resistance. We cannot assume there is no air resistance, however it is low enough not to make a difference in the long run.

The initial height of the projectile is from the ground, thus 0 metres in displacement in the y component. This is not exactly how our cannon operated however, because we raised up the opening where the cannon ball was shot out by about 25 cm.  As well, the optimum angle to shoot the cannon ball at is 45°. This is explained due to the parabolic motion of the cannon ball. The cannon ball will not be shot too low (resulting in a short flying time) nor will it be shot too far up, resulting in a short distance traveled horizontally. If the cannon is shot at a great angle up (e.x. 80°  the range might just be close to 0 metres.) The projectile will be in a parabolic motion, therefore the maximum range might be obtained if the cannon makes a 45° with the ground.

Other factors can contribute to a greater range.  The cannon ball should be as light as possible. The force applied on the cannonball is constant. The mass of the cannon ball is inversely proportional to the acceleration. If the mass of the cannon ball is lighter, a higher acceleration will be achieved. Lastly, the projectile should launched from a longer barrel of the cannon, with more baffles.  more energy will be stored before the cannon is launched. The ethanol will have more surface area to spread over, and therefore it will have the ability to make more connections with air. By increasing the action force acting on the cannon, the reaction force will also increase (equal and opposite reaction force.) This exemplifies Newton's Third Law.

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