Ball bearings are used in bicycles, cars, etc., because –

Answer: (c) the effective area of contact between the wheel and axle is reduced

Ball bearings place small hard balls between the wheel (hub) and the axle, so the surfaces roll over each other instead of sliding. The balls touch the surfaces only at tiny points, so the effective area of contact is reduced. Friction falls and the parts wear out more slowly.

• ✓ (c) Rolling balls touch the surfaces only at tiny points, so the effective area of contact is reduced. The frictional resistance of sliding is largely replaced by the much smaller resistance of rolling.
• ✗ (b) Ball bearings are fitted to cut friction and wear. Increasing the effective contact area is the opposite of what they do.
• ✗ (a) The balls do not enlarge the contact between wheel and axle. They change sliding into rolling, which lowers resistance.
• ✗ (d) Option (c) correctly states the reason, so this option is wrong.

Remember · Ball bearings replace sliding with rolling. The balls touch only at small points, which reduces the effective contact area and friction. This is why they are used in cycles, fans and vehicles.

Question: UPSC Civil Services (Preliminary) 2013, General Studies paper. Explanation: Minimalist IAS, checked 25 Oct 2026 (how we verify). · Report an error