Could someone let me know why it is necessary to change from gear to gear ?What is the scientific foundation?
I heard " The higher your speed the higher your gear, the lower your speed the lower your gear"
Get on a mountainbike and change between gears. The same reasons apply to changing your car's gears and changing your bike's gears: you can't peddle fast than x, and you can't get away when the gears are too extreme.
The point is that humans and engines operate best at a certain cadence or RPM. If the engine spins too slowly, it can't put enough power down. If it spins too fast, components will endure too much stress, overheat and break quickly. A formula 1 car can rev up to 18000RPM, but the engine needs to be rebuilt after every race. A large truck only revs to about 2000 to 3000RPM, and while it's pretty strong, it can't go very fast.