A lever is a tool; force is applied to it to generate (make) motion around a fulcrum. The thing moved is called the load or the work. Depending on the lenght of the lever you get move force by taking a longer time to move the long lever. This means yuo need less force on a long lever to move the same amount of weight (work) as it would take with a short lever.
This is a basic idea of levers trade effort for the time it takes to get work done.
The handle bars are a lever. You apply force (pressure) at the handle grips and the lever turns around the the fork forcing the wheel to turn in the direction of the force.
If it has hand brakes, the brake lever is a a lever. When you squeeze the lever it turns around the joint or pin and pulls the cable (load or work). The Pulled cable activates the brake, Notice if you move your hand close to the pin joint you have to work harder than if you move your hand toward the end of the brake handle.
Gear shift, is similar to the hand brake. Apply press to the selector lever adn it pivots around the fulcrum joint or pin and pulls the cable (load) that set the postion of the gears.
A foot predal is a lever. When you press down on the pedal the axle acts a a fulcurm to turn the main gear (work or laod) which in turn moves the chain.
The bike its self is a lever. By adjusting your weight and pulling up you get the bike to poivt on the back wheel and lift the front tire off the ground.
This is a second class lever since the work (your weight) is between the fulcrum (rear wheel) and the force (hands on handle bars).
The principles you learn in school may one day save a life. When you find someone pinned under a car, recall that a lever multiples your strnght and you can lift that car with a long lever.
Remember levers when you have to open an can of food .....
You teacher is not being ridiculous (not rediculous).
