Ball Bearings in Mechanical Systems

Ball bearings reduce friction in mechanical systems by reducing the effective area of contact between the wheel and axle. Instead of a large surface area in direct contact (sliding friction), ball bearings create point contacts between the balls and the races, which results in rolling friction rather than sliding friction. Rolling friction is much lower than sliding friction, hence reducing energy loss and allowing smoother rotation. Option (a) is incorrect as the actual contact area is not increased. Option (b) is incorrect as the effective area is reduced, not increased. Option (d) is incorrect because option (c) correctly explains the mechanism. The principle is that rolling motion over multiple point contacts is far more efficient than sliding over a large surface, which is why ball bearings are crucial in reducing wear and improving efficiency.

Answer: (c).