Can Car

CAN CAR Essay Keaton Mertz
Simms-D

The goal of the can car lab was to create a rubber band-powered car that demonstrates Newton’s laws, and conservation of energy. The advantages of having a heavy rolling can is that I would have a lot of rotational energy and momentum, the disadvantage is the car has more static inertia. If the car has more static inertia, then it will be harder for the can to roll backwards at the end of its run. The factors affecting the can’s net force (once the rubber band is unwound, but when the car still has momentum) are, force of gravity, normal force, KE, rubbing friction (into heat), the re-winding of the rubber band, wind, and air resistance. The force of gravity and support force cancel out, the wind almost cancels the air resistance against the can, and the KE is a greater force at this moment than the air resistance, re-winding (PEe), and the friction. At this moment the car is able to go forward. The PEe rewinding gets greater as the can moves due to the amount of force need to spin the rubber band increasing. Force car pushes on road, for road on car and the Force popsicle stick in on to the can lid, force can lid pushes out on the popsicle stick.
The energy of the can car is conserved because the PEe i (initial kinetic energy equals zero) is equal to the combination of the PEe f and the KEf which goes into dissipative forces, thermal energy through friction, or the energy is wasted through slippage. In my can car a lot of force was dissipated, to the point that PEi was greater than Ef. The can starts moving because once the rubber band is completely twisted, the wound rubber band tries to unwind. It should be easier for the rubber band to unwind by rotating the can than rotating the weights. Cans do not roll back and forth, because (at least in a my big can) the rubber band has the least amount of tension when it is barely wound (meaning a small force in PE=Fd), due to not having very much PE the can can not overcome its own static inertia.
The diameter of the can has a direct relationship with the speed and distance that results from the can. I chose the larger diameter can. The larger the diameter of the can, the farther the can car will go, and the smaller the diameter of the can, the faster it will go initially. This is the case because if all variables of the two can cars are identical with the exception of the diameter of the can then one untwist of the rubber band will propel the can once around. With that said the can with the larger diameter will go a longer distance (due to the larger diameter) and the smaller diameter can will take less time to make one revolution and therefore will use all of its elastic potential energy faster, making it faster than the large diameter can. It is difficult to do both because it’s impossible to have a can that has both a large and small diameter, so it is a give and take selection. The weight of the can also affects the outcome, because the more weight the can has the more rotational momentum the can has, also a tight rubber band will allow the can to move faster, but a loose rubber band will allow one to spin the can more(greater distance).The amount of weight one has and the amount of rotations the can be spun are related directly.
Building this car was an effective way of understanding Newton’s three Laws of Motion and the Law of Conservation of Energy, because all of these laws are required for the desired results of the can car moving forward. An improvement I made during the trials was adding tape to one side of my can allowing both sides to have equal diameters keeping the can from rolling straight. A improvement I should have made was getting the counter weights further from the rubber band, the further the weights are the more you can wind the can due to W=force times distance. The can would have to work harder to flip my weights if the weights were drooping.