Final answer:
Brake drums must not have cracks that exceed certain dimensions relative to the width of the friction area, with older guidelines limiting crack lengths to five times side-to-side and seven to eight times deep, while newer suggestions are eight diameters side-to-side and fifteen deep. For hydraulic brake systems, Pascal's principle is used to calculate the force at the wheel cylinders based on pressure consistency throughout the system.
Step-by-step explanation:
The question regarding brake drums is related to vehicle safety standards, particularly in the context of engineering and mechanics. Brake drums must not have cracks exceeding certain dimensions relative to the width of the friction area to ensure proper brake function and safety. Although the specific length of crack permissible can vary based on regulations and the manufacturer's specifications, the traditional “rule of thumb” for crack length was five times side-to-side and seven to eight times deep relative to the diameter of the drum. Newer recommendations suggest that cracks up to eight diameters long side-to-side and fifteen diameters deep can be permissible. However, always refer to the latest safety standards and manufacturer guidelines when evaluating brake drum integrity.
As for the calculation of the force created at the wheel cylinders, this is an application of Pascal's principle in hydraulics. Given that a force of 100 N is applied to the brake pedal, which generates a force of 500 N at the pedal cylinder, and knowing the diameters of the pedal cylinder and the wheel cylinders, you can calculate the force at the wheel cylinders using the formula for pressure (Pressure = Force/Area). The pressure is consistent throughout the hydraulic system, so the force at the wheel cylinders can be found by rearranging the formula to solve for force at the wheel cylinders, taking into account the area difference between the pedal cylinder and the wheel cylinders.