A-friction:
The greater the friction between the supporting surface and the parts of the body which are contact to it, the more stable the body will be but up to certain limit
B-softness of the supporting surface:
More energy will be wasted if we use soft matters so hard matters should be used to increase stability
C-inclination of supporting surface:
Inclination of surface:
The angle which the supporting surface makes in relation to horizontal it called (friction angle)
The greater the inclination, the less the stability
5-segmentation principle:
"If there is a deviation of apart in the body to certain direction, there is another compensatory deviation of another part of the body to the opposite direction to maintain balance during this position"
6-subject state:
a-mass: the greater the mass of the body, the will be its stability
B-vision: greater balance and stability when he focuses his vision on a stationary object rather than on moving or disturbing one
C-physical or emotional state:
Positive relationship between emotional state and ability to maintain balance
D-age: person will be more stable in adulthood period than in childhood and stability will decrease
E-speed: easier to balance on a bicycle when it is moving fast than when it is traveling slowly
Equilibrium
Definition:
State of balance in which all forces are equal
The body is in equilibrium when the resultant of all forces acting upon it is zero
Types of equilibrium:
1-stable equilibrium:
If the object is placed slightly and it tends to return to its original position, equilibrium is stable
The COG has to be raised before the line of gravity will fall outside the original BOS
If line of gravity falls outside the BOS, the object will fall
Increase BOS will increase stability:
2-unstable equilibrium:
If the object is displaced slightly and it tends to increase its displacement, equilibrium is unstable
3-neutral equilibrium:
If it comes to rest in anew position without a change in the level of the COG either upwards or downwards when it is displaced
Condition of equilibrium:
1-static or translational equilibrium:
If the body at rest with velocity equal zero, the sum of all forces acting on the body equal zero
_________________
اللهم احسن خاتمتنا فى الامور كلها
وأجرنا من خزى الدنيا وعذاب الاخره
موضوع: رد: تلخيص البيو ميكانكس 
السبت سبتمبر 08, 2007 7:17 pm
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