Biomechanics Flashcards
Mass
The amount of matter an object is made up of
inertia
The tendency for an object to resist its change in emotion.
relationship between mass and inertia
the greater the mass of an object the greater its inertia.
force
force (definition, equation, how it affects objects)
force= mass x acceleration
- force can be described as a push or pull on an object
1. changes the shape of an object
2. change an objects motion/speed (acceleration, negative acceleration)
3. change an objects direction
internal force
internal force can be described as muscles pulling on bones at a joint.
external force
- AIR AND WATER RESISTANCE (DRAG FORCE) is a frictional force that occurs when one of the surfaces is air or water.
drag force opposes the direction of motion. - FRICTION occurs when two surfaces contact each other.
- GRAVITATIONAL FORCES is when there is a constant downward force acting on objects at 9.8m/s
motion definition and the 3 types
refers to the change in position of an object/body in relation to time.
- linear motion
- angular motion
- general motion
acceleration
definition and equation
an object positively changing its motion. change in velocity over a period of time
- acceleration = change in velocity/change in time
deceleration
something decreasing motion
velocity
definition and equation
speed with direction. Time taken to change position
- velocity = displacement/time
linear motion
something moving in a straight line or curved path. all parts travel the same distance at the same time in the same direction.
angular motion
- when a body part rotates around its central axis
- an object/body twist or rotates around an axis
Newtons first law of inertia
an object will stay at rest or continue to travel in the same direction at a constant velocity unless acted on by an unbalanced/external force.
1. the greater the mass of an object the greater the inertia hence the more force required to change the motion of the object with a greater inertia.
2. If an object is at rest (no motion) it will remain at rest.
3. If an object is in motion, it has a tendency to remain in motion
Newton’s second law of force and acceleration
The rate of acceleration of a body/object is proportional to the force applied to it and the direction to which the force is applied (force= mass x acceleration)
Newton’s third law of Action/Reaction
when two objects come in contact with one another, they exert forces that are equal in size but opposite in direction to each other. For every action, there is an equal and opposite reaction.
moment of inertia
resistance of a body to change its angular rotation
linear momentum
definition and equation
objects with greater momemtum are harder to stop
mass x velocity
- if an object is stationary it has zero momentum
- if ojects have the same mass, the object with greater velocity will have the greatest momentum
- if two objects have the same velocity, the object with the greatest mass will have the greatest momentum.
angular momentum
equation
angular velocity x moment of inertia
angular velocity
rate of rotation around an axis, measured in RPM
Conservation of momentum
- when two objects come into contact the total mmomentum that existed before the collision equals the total momentum after.
- momentum is trandferred from one object to another depending which objects has teh greater mass/velocity. However momentum post contact is conserved.
impulse
definition, equation
impluse= force x time
- appling force for longer (impulse) results in a change of momentum.
- impulse can be applied to an object to either increase or decrease the momentum of the object
injury prevention
absorbing force over time (force x time) will decrease the momentum of an object or body. the force is absorbed overtime
eg a crash mat will absorb the impact force over a longer period of time, they will still come to resr but with less risk of injury because of the smaller impact force.
Summation of momentum
summation of momentum
1. BODY PARTS use as many body parts as possible
2. SEQUENCE- move larger (slower) stronger body parts first eg quads. followed by the smaller (faster) body parts eg hand
3. TIMING move the next body part, only when the previous part has reached maximum velocity
4. STABILIZATION - body parts must be stabilised so that momentum is not lost.
5. appropriate follow through to avoid decleration and loss of momentum
Application of summation of momentum
- activate larger body to smaller body parts in a sequence
- this will increase impulse (fxt) as force is being applied for longer
- greater impulse (fxt) will result in an increase in momentum (mxv) and velocity of body parts
- increases agular velocity and momentum of the arm and transfers to the ball
- increases linear velocity of the ball
- ball will fly further and faster
Projectile motion
definition
when an object is launched into the air, it becomes a projectile that is affected by air resistance and gravity
Path and distance are impacted by these 3 factors
- speed of release
- angle of release
- height of release
Angle of release
release height and landing angles
45 deg if landing is the same and release height. less than 45 deg if release height is above landing height. greater than 45 deg if release heigh tis lower than landing height
factors influencing projectile motion
- velocity
- mass
- shape
- surface area
- nature of surface area
how do you improve balance and stability
- lower your centre of gravity by bending your knees
- widen your base of support by taking feeting further apart
- ensure line of centre of gravity is withing base of support
describe first clss levers (type)
one example
levers have the axis as the central componemnt that separates the force and resistance RAF eg crow bar
describe second class levers (type)
one example
levers have the resistance as the central component that separates the axis and force ARF eg plantar flexion in a calf raise
describe third class levers (type)
an example
levers have the force as the central component that separates the axis and the resistance AFR eg throwing a ball
what do 1st and 2nd class levers do
- assist in decreasingteh amount of force required to move a mass
- FORCE MULTIPLYER
- more force can be applied for less effort
- mechanical advantage of more that 1
force arm
definiton
distance between the axis and the force
resistance arm
definition
distance between force and the resistance
what do 3rd class levers do?
increase the speed and ROM at the end on the lever
SPEED MULTILIERS so have a mechanical advantage of less than 1
- increase the length of the resistance arm enabling the athelete the increase ROM at the end of the lever therefore increasing the speed/velocity at the end of the lever
- thisallows for greater linear velocityto be transferred to objects upon contact achieveing increased speed/distance
- the longer the resistance arm, the greater the inertia that needs to be overcome.
example of a 3rd class lever is a soccer kick. explain
- decreasing the moment of inertia and resistance arm enables the leg to be swung through more quickly with greater angular velocity.
- increasing the length of the resistance arm increases the ROM at the end of the lever, Ball will travel with greater linear velocity.
distance
definition
path travelled by an object from start to finish, regardless of the direction travelled
displacement
definition
change in position of an object from the starting position to the finishing position
speed
def and equation
time taken to cover a certain distance m/s
- speed = distance/time
