Final answer:
Spring brakes are applied by a means other than air, electrical, or hydraulic systems; they use the potential energy stored in springs. Hydraulic brakes operate on Pascal's principle, while regenerative brakes convert kinetic energy into electrical energy.
Step-by-step explanation:
Spring brakes are applied by a means other than air, electrical, or hydraulic. This is because spring brakes are mechanical brakes that use the potential energy stored in compressed springs to apply force.
When the spring brakes are activated, the energy from the springs is released, applying the brake pads to the wheel to slow down or stop the vehicle. This is in contrast to hydraulic brakes that use Pascal's principle, where a force applied at one point is transmitted to another point using an incompressible fluid, multiplying the force in the process. Regenerative brakes are another type of braking system that slow a vehicle by converting its kinetic energy into electrical energy, which can then be stored in a battery.