Methods of Reducing Friction

Methods of Reducing Friction

Although friction is essential in sport, there are many situations where it must be reduced to save energy, cut wear, or let equipment and the body move more efficiently. The CBSE Class 12 Physical Education textbook gives four main methods, each working on a different one of the factors — surface roughness, contact type, or shape — that friction depends on.

• Polishing — polishing and rubbing a surface smooth removes the microscopic irregularities where two surfaces actually interlock, lowering unevenness and so reducing the frictional force between it and whatever it contacts. Example: shining one side of a cricket ball increases the ball's swing, because the smoother shiny side moves through the air with less resistance than the rough seam side, creating an air-pressure difference between the two sides of the ball.
• Lubricating — applying a lubricant such as motor oil, grease or wax between two surfaces creates a thin film that stops the surfaces gripping each other directly, converting most of the friction into a much smaller fluid friction within the lubricant itself. This is a common way to cut friction in mechanical systems such as bearings and gears, and in sport is seen in waxed skis and snowboards, where wax reduces friction between the base and the snow to increase glide speed.
• Using wheels and ball-bearings — it is far easier to roll an object than to slide it, because wheels and ball-bearings convert sliding friction into rolling friction, which is almost always much smaller for the same surfaces and load. This reduces friction between the contact surfaces and saves both energy and time. Example: in roller skates and skateboards, both the wheels and the internal ball bearings work together to reduce friction and allow a smooth, fast ride; bicycles use the same principle at the wheel hub and pedal crank.
• Streamlining — friction due to air, a form of fluid friction, is cut by shaping the body or object so air flows around it smoothly instead of becoming turbulent. Example: the javelin, boats, ships, racing cars and cyclists' helmets are all given a sharp, tapered or curved shape to reduce air resistance and move faster for the same effort.

Why this matters in sport …