BIOMECHANICS TEST 3
Four function of simple machine
1. balance two or more forces 2. provide advantage in force 3. provide advantage in linear range of motion and speed of movement 4. change the effective direction of the applied force
Three Characteristics of force
1. magnitude 2. direction 3. point of application
Moment of inertia depends on which factors
1.quanity of rotating mass 2. its disturbution around the axis 3.Mass 4. r= perpendicular distance between the mass particle and axis or rotation
Produces balanced movements when axis is midway between force and resistance
1st
can serve all four functions of a simple functions
1st
neck extensors and cervical extension
1st
seesaw
1st
Crowbar
2nd
favors force production
2nd
force lever arm will always be longer than the resistance lever arm. ( smaller force an move larger load)
2nd
most efficient configuration but least common within the body
2nd
produces force motion when axis is close to resistance
2nd
pushup
2nd
raising body up on toes
2nd
resistance is always closer to axis than the force
2nd
wheelbarrow
2nd
Favors resistance advantage as well as speed and ROM
3rd
biceps in elbow flexion
3rd
hamstrings contracting to flex at knee while standing
3rd
lever of force is always closer to the axis
3rd
most common in the body
3rd
produces speed and ROM when axis is close to force
3rd
requires a great deal of force to even move a small resistance
3rd
resistance lever arm is always longer than the force lever arm
3rd
Most resting muscle have and angle of pull?
< 90
Short lever arms enhance_____ while sacrificing ______&________
Angular velocity, linear speed, ROM
Define and State the Equation for Momentum
Any change in momentum is equal to the impulse that produces it force applied in direction of motion will increase momentum. Force applied in the opposite direction of motion will decrease momentum
What principle explains why some things float and some things sink? buoyancy
Archimedes Pricniple
Fluid forces buoyancy drag and lift do not regard he same laws amd principles of normal forces
Fasle they do
Parallel Forces
Forces not in the same action line but parallel to each other Ex: two forces upward one downward
Define Force
Is that which pushes or pull through direct mechanical contact
Newton's first law of motion
Law of Inertia and object at rest remains at rest and object in motion stays in motion unless acted upon by an outside force F=/ 0
Newtons 3rd law of motion
Law of reaction for every action there is an equal opposite reaction F=-F
If an angle of pull is less than 90 degrees then _____ force is directed towards the _____ and help stabilizes_____.
Non-rotary, fulcrum, joint
Work
W=Fs work is the product of force expended and the distance over which force is applied
Concurrent Forces
act at the same point of application at different angles
muscular angle of pull is the ________ between the line of pull and mechanical axis of the bone.
angle
What is the product of moment of inertia (I) and angular velocity (w)
angular momentum
angle of pull > 90
dislocating force is directed away from fulcrum does not occur often
A force whose direction is not line with the center of gravity of a freely moving object or the center of rotation of an object with a fixed axis of rotation is called
eccentric force
Specfic gravity <1
floats
angle of pull 90
force is all rotary
Linear Forces
forces apllied in the same direction the resultant is the sum of the forces
X-axis
horizontal component is always the axis of the bone non-rotary component
For perfectly elastic objects the angle of ____ is equal to the angle of _______
incidents, reflection
Lever
is a simple machine consisting of a rigid bar that rotates about fulcrum
Laminar Flow
is a smooth unbroken flow of fluid around a object
Elasticity
is the ability to resist distorting influences and to return to the original size and shape
energy
is the capacity to do work
Force Couple
is the effect of equal parallel forces acting in opposite direction
Potential Energy
is the product of weight of an object and the distance over which it can act
Drag
is the resistance to forward motion through a fluid
Newton's second law of motion
law of acceleration and object is directly proportional to the force causing it and inversely proportional to the mass of the object F=ma
the amount of torque is determined by
length of moment arm or force
When force is applied in line with a freely moving object center of gravity
linear motion occurs
Composite forces on the body are classified as what according to their direction and application?
linear,concurrent, or parrael
I= Emr^2
m=Mass r= perpendicular distance between the mass particle and axis of rotation
Torques are vector quantities which means in regards to summation of torques what must be considered
magnitude direction point of application
Free body Diagram
magnitude, direction, point of application, weight (m), Reactive force (R), friction(f)
the perpeidicular distance between force vector and the axis is called
moment arm
clock wise torque sare
negative
The sum of two or more torques may result in
no motion linear motion or rotary motion
What component of the force is the only factor in torque production?
only rotary component
For muscular force_________ between the line of force and the mechanical axis of the bone joint angle.
point of application
What type of motion occurs when the force applied is directed through the center of gravity of an object?
point of application
counter clock wise are
postive
power
rate at which work is done
Specific Gravity
ratio of the density of an object to the density of water
Density
ration of weight of an object to its volume
angle of pull 45
rotary and non rotary components are equal
Direction of a muscular force vector is in the________ of the line of pull of muscle
same direction
Specfic Gravity >1
sinks
stress and strain are defined as
stress is the force that acts to distort strain. Strain is the distortion that occurs
magnitude is?
the amount of force being applied EX: BENCH PRESS
The larger the angle of pull from 0-90 ?
the greater the y and less the x component
Ft=m(Vf-Vi) define and state the name of this equation
the product of mass and velocity and it is the equation for momentum
Coefficient of friction
the ratio of force needed to overcome the friction, to the force holding the surface together W
in regard to the principles of torques resultant torques in a force system must be equal to the sum of the torques of the individual forces of the system about the same point
true
shortening the radius of rotation increases the moment of interia and increases the angular velocity
true
the greater the distance of the fore arm the more torque produced by the force which results in increased leverage so we can move large resistance more easily
true
Y-axis
vertical component is always perpendicular to the mechanical axis of the bone rotary componet
