Final answer:
The force that pushes the brake cylinder piston back when the brakes are released is supplied by hydraulics.
Step-by-step explanation:
The force that pushes the brake cylinder piston back when the brakes are released is supplied by hydraulics.
In a hydraulic brake system, the force applied to the brake pedal is transmitted to the master cylinder, which then increases the force by using a lever and hydraulic system. This increased force is then transmitted to the slave cylinders or wheel cylinders, which push the brake piston back.
By using Pascal's principle, the pressure created in the master cylinder is transmitted equally to the slave cylinders, resulting in the same force output at each wheel cylinder.