Usually an aluminum alloy, although high-end ones may be of titanium.
They are exposed to the weather and are not made of a rust-proof metal.
Brakes - the rider just put feet on ground to stop
Bicycle brakes allow the rider to slow down in a controlled manner and with out undue wear on the tires.
It is your momentum of moving forward that has to be overcome before your brakes can bring the bicycle to a stop.
Brakes turn kinetic energy into heat.
Using brakes slows your speed.
A tutorial on how to adjust bicycle front cantilever brakes can be found on Youtube in the form of a video outlining the key steps one should take to adjust the bicycle front cantilever brakes.
THe brakes rarely need to stop. But the brakes can be used to make the bike stop.
Brakes help a bicycle to stop, of course --- but do you know why? it's because brakes use friction. When you squeeze the brakes, rubber blocks press against the wheels. The friction between the blocks and the wheels slow your bicycle down.
Bicycle hydraulic brakes offer better braking performance, more precise control, and require less maintenance compared to traditional cable-actuated brakes.
Depends on the type of brakes, but most bike brakes would use levers.
They get warm and wear when used.