Question

Reflecting on the Activity and the Challenge Many athletes seem more concerned about their shoes than most other items of equipment, and for good reason. Small differences in the shoes (or skates or skis) athletes wear can affect performance. As everyone knows, athletic shoes have become a major industry because people in all "walks" of life have discovered that athletic shoes are great to wear, not only on a track but, as well, just about anywhere. Now that you have studied friction, a major aspect of what makes shoes function well when need exists to be "sure-footed," you are prepared to do "physics commentary" on athletic footgear and other effects of friction in sports. Your sports commentary may discuss the u of the shoe, the change in friction when a playing field gets wet, and the need for friction when running

Answer 1

We know that, the letter "_$\mu$" is used in physics which means the "coefficient of sliding friction".

Mathematically, we have

_$\mu$ = (force required to slide object on surface at constant speed) / (perpendicular force exerted by the surface on the object)

It does not have any units. Basically, it is expressed in decimal form. It is valid only for the pair of surfaces in contact when

the value is measured. Only when sliding occurs on a horizontal surface and the pulling force is horizontal or perpendicular force that the sliding object exerts on a surface which equals to the weight of an object.

When a force is applied to an object, then the resistive force of friction acts in an opposite direction & parallel to the surfaces.

Friction plays a big role in sports. The motion of a skier and friction are parallel to the slope and so it is most convenient to project all forces onto a coordinate system where one axis is parallel to the slope and the other is perpendicular.

Our sports commentary on the "_$\mu$" of the shoe, the change in friction when a playing field gets wet and the need for friction when running. What happens when a runner tries to change his direction of motion on a wet surface :

• As he plants his foot to slow his motion, the coefficient of friction between the turf and him is reduced by the water on a surface.
• The reduced coefficient of friction decreases the frictional force.
• The decreased frictional force makes it harder for him to stop motion his to the right.
• The runner loses his footing and falls.