WEEK 11 of MECHANICAL BASES Flashcards
(49 cards)
define fluid mechanics
the branch of mechanics about the forces that fluids exert on the object in them or moving through them
in human movements it is, air, water and exert forces on the body
describe how aquatic sports relates to fluid mechanics
fluid forces are large and their effect is obvious
describe fluid mechanics in land based sports
the effete of fluid forces may be so small that their effects can be largely ignored in biomechanics calculations
OR the effects can be so large that its influence on performance is obvious
describe air resistance in relation to fluid mechanics
in some activities such as hang gliding and sky diving, human life depends upon the effects of air resistance
define ‘solids’
the solid molecules are arranged in a lattice, and the molecules movement is restricted
define ‘liquids’
the liquids molecules have a constant space between them. the molecules can move with respect to each other when a shear force is applied
define ‘gases’
the gas molecules are arranged variably and are also much wider
describe fluid (x2)
- a substance that flows due to deformation when subjected to shear stress
- both gases and liquids are fluids with similar mechanical behaviours
describe the two factors fluid as a continuum is seen as
1) each and every molecule
2) the average effect of all molecules= this means that the fluid can be regarded as a continuum
what are the 2 fluid properties and define them
1) viscosity= the rate of fluid deformation
2) density = mass in given volume
define fluid viscosity
a property of fluid. the rate of deformation of the fluid when shear stress is applied
- honey or oil has a high viscosity as it takes a long time for it to flow down to an inclined surface
define water viscosity
water has a low viscosity as it flows rapidly down an inclined surface.
define and describe fluid density measurement terms
def= the mass per unit of volume
P= m/v
what are the two influences on fluid properties and how
1) pressures which effects both density and viscosity
2) temperature
this increases temp which then increases motion therefore decreasing density and viscosity which therefore increase the viscosity of gas.
describe hydrostatic pressure ( x4)
- the force exerted by a fluid
- P=f/a
units= n/cm - both density and viscosity decrease at a low pressure
define the relationship between density and altitude
the density of a column of air decreases as altitude increases because air expands as pressure decreases
define the atmosphere
pressure gradient= particles always want to go from a high to low pressure situation
define influencing pressure with snowshoes
snow shoes prevent the person from sinking into soft snow because the person weight is spread over a larger area, which reduces the pressure on the snows surface
describe pressure and water depth (x2)
- pressure increases with water depth
- pressure increases by 100kpa for every 10.06m of depth
define buoyancy and describe what its the product of
def= an upward force that opposes weight
product of the displaced volume and specific weight of the fluid
describe buoyancy and a hot air balloon
buoyancy is one of the few factors that lift upwards and fights gravity. buoyancy also acts in the air, such as a hot air balloon. the hot air balloon weighs less than the surrounding air, this results in a buoyant force that acts upward
describe centre of buoyancy (x2)
- the place where the buoyant force concentrates is called the centre of buoyancy
- the place where buoyant force acts is also the objects centre of volume
describe the relationship between centre of buoyancy. and flotation (x2)
- the centre of buoyancy acting upwards is higher on the human body than the centre of gravity which is acting downwards
- these two forces cause rotation, dropping the legs down and lifting the chest upwards
identify what happens when centre of gravity versus the centre of buoyancy
when the two forces are aligned above and below each other, rotation ceases.
