exam 2 Flashcards
Newton’s First Law
law of inertia: maintain a state of rest pr constant velocity unless acted on
*just a concept so has no units
Newtons Second Law
Law of Acceleration
* F=ma
-force applied to a body causes an acceleration of that body of a magnitude prop. to the force
Newton’s Third Law
law of reaction
-for every action there is an equal and opposite reaction
mass`
the quantity of stuff
-Slug or Kg
-no direction
-nothing to do with gravity
Force
a push or pull on a body
-Vector
-lb or Newtons
Newton Units
kgm/s^2
Weight
the amount of gravitational force excerted on a body
-Wt=mg
Pressure
Force/area
-Pa or psi
-N/m^2`
Stress
when the loads are inside the body
Torque
the rotary effect of a force
-T=Fd
-Nm or Ft lb
First class lever
applied force and resistance are on opposite sides of the axis (seesaw)
Second Class
Applied force and resistance are on the same side of the axis, but resistance closer to axis (wheelbarrow)
-Mechanical advantage >1 so can move more force
Third Class
Force and resistance are on same side, but the force is closer to the axis this time (muscle-bone)
-Mechanical advantage <1 so has greater range of motion
Impulse
the product of a force and the time over which it acts
-J=Ft (Ns or lb s)
Density or specific weight
Mass/volume
Compression
pressing or squeezing force through body
tension
pulling or stretching force through the body
-muscles pulling on the skeleton
Shear
force directed parallel to the surface of a body
-knee in squat position
Bending
3- point load
-asymmetric loading that produces tension on one side of the longitudinal axis and compression on other side
Torsion
twisting force
Acute Injury
left side of curve
-one loading cycle with severe injury
Overuse or Chronic
right side of curve
-multiple loads overtime
