friction

ib sports science HL

friction

friction

a force between 2 contacting objects that acts parallel to the interface and in opposition to the relative motion

value of friction

f=CoF×reaction force

dynamic friction

friction of a moving object

static friction

friction of a stationary object

coefficient of friction

the value that objects have depends on how “sticky“ they are. For instance ice has a lower CoF than rubber. ratio of frictional force to gravitational force

coefficient of static friction

is a measure of the force required to initiate the movement of an object at rest relative to another surface.

coefficient of dynamic friction

reduces the force required to keep an object moving

magnitude of CoF

depends on the interaction of 2 surfaces in contact. The greater the contact, the greater the CoF. Usually between 0 to 1, but can be greater than 1. This means that it would take more force to slide something than picking it up

friction in sports positives

friction provides grip and traction, which are crucial for stability and control in many sports.

friction in sports negatives

Exessive friction can lead to loss of energy, decrease in speed, and increase wear and tear equipment and surface

Maximizing friction

Wax on skies, rubber on wheels, skates on ice, golf gloves.

minimizing friction

aerodynamics of equipment.

safety and friction

prevent slips and falls, some surfaces can cause injuries in knees and ankles due to exess friction

drag

the force acting to oppose the motion of an object through fluid medium like water/air. The coefficient of drag increases as your velocity increase

form drag

reaction of fluid when a body pushes against it. By streamlining the body and minimizing the surface area facing the direction of the motion, this type of drag is reduced.

surface drag

outer surface of body catches a layer of neighbouring fluid as it moves. Can be minimized by changing the surface to reduce the interaction between surface and fluid.

wave drag

caused by the displacement of fluid (usually water), as the body moves along the surface. Wave drag can be reduced by avoiding motion at the interface between air and water.

factors influencing drag

shape/size of the object, density of the fluid, velocity of the moving body, surface area of the object, equipment, viscosity.

Outline different types of drag and ways they can be reduced in swimming. [6]

Surface drag:

outer surface of body catches a layer of neighbouring fluid as it moves

reduced by creating smooth surface / shaving / shark suit

Form drag:

reaction of fluid when a body pushes against it

proficient / streamlined swimming technique reducing turbulence

Wave drag:

caused by the displacement of fluid (usually water), as the body moves along the surface

swimming underwater for as long as possible

wave-less pools designed to reduce wave drag

Analyse factors that decrease drag for a road cyclist. [5]

a tucked body position decreases surface area/size while cycling decreases drag;

decreased opposing wind decreases drag;

clothing such as tight apparel will decrease drag;

equipment for cycling such as appropriately designed/aerodynamic helmet and bicycle will decrease drag;

avoidance of turbulent air/drafting/being behind the athlete in front decreases drag;

shaving/waxing skin has a positive effect on reducing drag;

lower speed decreases drag

Outline how drag can be changed to maximize performance. [4]

change the shape/texture of the equipment to reduce surface drag

reduce surface area in contact to reduce form drag

decrease the density of the fluid can decrease wave drag

A smooth surface can allow the fluid to flow more easily, reducing drag.

Discuss factors that can affect friction in sport. [4]

1. Roughness/smoothness of the surface

2. shape or design of the object/equipment

3. Sliding surface’s state of matter (solid/fluid)

4. Temperature