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Point around which a bodys weight and mass are equally balanced in all directions
from a kinetic perspective, the location of the center of gravity determines the way in whcih the body responds to external forces |
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the quantity of matter that comprises a body
Metric (kg), kilogram
English system, slug, larger than a kg |
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Resistance to acceleration, tendency of a body to remain in its current state of motion wether motionless or at a constant velocity unless actoed on by an outside force
no unit of measurement
proportional to mass, the highter the mass the harder it is to disrupt |
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Push or pull acting on a body charactorized by its magnitude, dirction and point of application to a given symbol
Metric, newton (N)
English (lb)
force = mass x acceleration
1 N = 1kg x 1m/s2
1lb = 1 slug x 1 ft/s2 |
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Definition
overall vector sum of many froces acting on a body.
When all froces cancel each other out, the net result is that the body remains in its original state of motion
When a net force is present, the body moves in the direction of that net force w/ an acceleration proportional to the magnitude of the net force |
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Force over a given area
metric n/cm2
english lb/in2 (psi)
Pressure= force/area |
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amount of gravitational force exerted on a body
metric, N
English, lb
Weight is mass x acceleration due to gravity
wt= mag
ag=-9.81m/s2 or -32ft/s2
the- vector indicates that it is going down towards the earth |
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The amount of space an object occupies
volume is considered to have 3 dimensions heigth, width, and depth raised to an exponent of 3
metric units, cm3, m3, and liters (l)
english units in3, feet3, and quarts (qt) |
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Mass per unit volume
symbol, rho, magnifying glass
amount of given material in a certain volume
formula rho = mass/volume
metric units, kg/m3 (some mass/some vol)
english, units are not commonly used |
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weight per unit volume
proportional to density bc weigh and mass are proportional to one another,
metric, n/m3
english lb/qt3 |
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when sufficient force is applied though a point other than the center of an object, the object undergoes both tranlation and rotation
The rotary effect created eccentric force is known as torque
torque is the angular equivilent of linear force
(T)= Fx perpendicular distance (dperp)=d1
metric units, newtonsxmeters (Nxm)
english units ftxlb
Always a rotational movement
all muscles produce force and the end result is torque |
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Definition
when a force is applied to a body, the result is dependent on both the magnitude of the force and the duration that it is applied
the product of force and time is known as impulse
impulse = Fxt force x time
metric units, N-sec
english, lb-sec |
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Definition
the effect of a given force depends on its direction, duration, and magnitude
compression
tension
shear
stress
bending
torsion |
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squeezing force, the weight of the body acts as a compressive force on the bones that support it
ex. the adjacent vertebrae with a disc between them |
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pulling force creating tension in the object to which is applied, opposite of compression
muscles produce tensile force that pulls attached bones
ex, when things are bent they produce compression forces on one side and tensile forces on the other |
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acts parallel to a surface
causes on e portion of an object to slike or displace w/ respect to another portion of the object
during a squat exercise, the joint shear is greatest at the full squat position, this places a large amount of stress on the ligaments and muscle tendons |
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resulting force distrabution inside a body when an external froce acts
Quantified the same way as pressure, a given force acting on a small surface provideds greater stress than the same force acting over a large surface, usually on the inside while pressure is on the outside, stress is a result of an outside pressure |
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| when eccentric force is applied to a structure, the structure bends creating tensile stress on one side and comprhensive stress on the opposite side |
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occurs when a strucure is forced to twist about its longitidinal axis, typically when one end of the structure is fixed
Torsion fractures of the tibia accur when the foot is held in place while the body rotates |
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| results of force application |
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| factors that influence whether in injury occurs |
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Definition
| magniude and dircetion of the force, area of force distabution, material properties of the loaded body tissues |
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| know the load deformation curve |
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| elastic region, plastic region, yeild point, ultimate failure point |
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