A MotoGP race bike is a marvel of engineering that costs as much as a good size house in San Fransisco to develop and build. It is one of the fastest machines on wheels, capable of 210+ mph speeds and able to keep traction and grip the track at lean angles that pass 60 degrees. For a scientist, motorcycles and superbike racing are a perfect kinetic demonstration of the laws of physics. Only in racing a mistake has a much more dramatic result than in the lab.

The first lesson to consider as you take a nice fast sweeper or watch your favorite star diving into a corner is Newtons first law of motion, “An object in motion tends to stay in motion with the same speed and in the same direction unless acted upon by an outside force.” To you the rider or spectator, this means the faster the motorcycle is going, the less it wants to turn. Converting the bikes energy from a straight ahead motion to turning requires a negotiation with physics.

First a rider countersteers (pushes the handlebars away from the direction of the turn), because the wheels are acting as gyroscopes this causes the bike to lean in the opposite direction (into the turn) narrowing the contact patch (between the tyre and road) and making the motorcycle easier to turn.

Second the rider shifts their weight off the bike in the direction of the turn. The bike is already able to turn well because of the lean angle caused by countersteering, the change in riders weight moves the center of gravity and allows the motorcycle to stay more upright. At the point of maximum lean required to get through a turn at the maximum speed, centrifugal force wants to pull the motorcycle of the track, the rider is using traction, momentum, and gravity to stay on course.

Newtons Second Law explains why the motorcycle moves at all: ” a force applied to an object will cause it to accelerate.” This will happen until the rider runs out of track or other forces such as wind resistance vs acceleration become balanced.

With today’s MotoGP machines and late braking riding styles, these motorcycles must be able to go from 200+ mph to 40 mph very quickly. The brakes use friction to accomplish this, primarily on the front brakes of motorcycles. All the energy is transferred to the brakes in the form of heat thanks to the conservation of matter and energy law. A major issue that arises from this is some of the heat is transferred to the hydraulic-brake fluid causing a loss in stopping power, which can have disastrous results for a rider. Engineers have come up with special ceramic materials to combat this and riders have become used to getting on and off the brakes quickly.

To be successful at racing you want to push these rules as far as you can without actually breaking them. Their is a very fine line between the best cornering and crashing, a line where outward, downward, and forward forces balance precisely. Go beyond it, breaking these rules, leads to broken motorcycle parts and ego’s. Class Dismissed!

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