AUTOMOBILE - LAB

OBJECTIVE:
Identify where car power comes from, and why.

BACKGROUND:
A car is a complex compound machine, that is fueled by gasoline to create motion. In a car, the engine is responsible for producing the power that causes the wheels to turn.  The engine turns a rod called a crankshaft which is connected to the drive shaft which in turn is connected to the axle which of course is connected to the wheels.

Gasoline is pumped into the gas tank of the car.  From the gas tank, the fuel travels through the fuel line and reaches either the carburetor or fuel injector.  From this point the gas flow is controlled by the amount of pressure placed on the accelerator.  The fuel is converted into a mist much like a perfume by the carburetor.  This "perfume" is then released into the cylinders where it is compressed, ignited, and exploded.  Each time an explosion takes place the pistons are forced down, causing the crankshaft to turn.  With each turn of the crankshaft comes a turn of the driveshaft and with each turn of the driveshaft, comes a turn of the axle and consequently the wheels.

A car is a complicated and complex machine that is dependent upon the laws of physics for both efficiency and performance.  Nearly all the laws of physics can be found in the workings of an automobile.  Friction between the rubber tires and asphalt ground is the reason why the car moves (aside from all the workings of the engine).  To better improve  friction, tires are built and designed with tread patterns that grip the asphalt road more efficiently. 

Aerodynamics is also a great factor when it comes to designing cars.  Air resistance can contribute greatly to low gas mileage and poor efficiency.  As a result, car manufacturers design automobiles with pointed fronts, rounded bodies, and streamlined patterns.  With these designs the air can be "cut" so that it does not act like a block stopping the car.  A good way to test the notion of air resistance is to put a hand out of a car when going down the freeway.  A vertical hand pointing straight up will encounter great air resistance while a horizontal hand will encounter hardly any.  This is the reason why cars are pointed in the front and not flat. 

Work done by the engine is transferred to different parts of the car through gears and levers until this work reaches the axle.  Once the work has reached the axle the tires can be turned and the car can move.  For this work to be created, however, requires the presence of such items as  carburetors, pistons, crankshafts, spark plugs, gasoline, and many other components.  A car is about the best example of all the forces of physics coming together for one purpose, motion.