Biomechanics Flashcards
Motion
Refers to the change in position of a body in relation to time.
A body is either in a state of rest (not moving), or state of motion (moving)
Linear Motion
Motion that occurs in a straight line or curved path.
Rectilinear - straight path
Curvilinear - curved path
Angular Motion
Motion that occurs when a body moves along a circular path (around some type of axis)
- External: outside of the body
- Internal: within the body, joint or body part rotation
General Motion
A combination of both linear and angular motion
- most sporting examples
Mass
Quantity of matter found within a particular body, does not take gravity into consideration.
Relationship between amount of Mass and Inertia
If an object has greater mass, it has more inertia, and therefore harder to move.
Less mass = less inertia = easier to move
Weight
The force of gravity on an object
- weight = mass x gravitational acceleration
Inertia
The resistance of a body to a change in its state of motion.
Body at rest = reluctant move
Body moving = reluctant to change its direction or velocity.
Forces that act upon an object that change its stage of inertia:
- air resistance, friction, wind, gravity, applying a force greater than its mass
e.g., when a ball is in the air, gravity can pull it down.
- a ball rolling down a hill will continue to roll unless friction or another force stops it.
Force
Is an effect on one body that results from the interaction of a second body.
Unit of measure = Newton (N)
F = mass (m) x acceleration (a)
- the more mass, the more acceleration = produces more force, which is then transferred to object causing a change in movement.
To change the state of a body, force must be applied to it:
- a force can either have a pushing/pulling effect on a body, causing it to accelerate, decelerate and/or change direction.
- sufficient force must be applied to overcome the inertia of the body.
Momentum
The rate of motion a particular body of mass has
Momentum (P) = mass (m) x velocity (v)
higher to mass + higher the velocity = greater the momentum, but inertia must be overcome first
Angular Momentum
A product of moment of Inertia and angular velocity.
H = I x w
Momentum around some form of axis
e.g., diving, figure skating.
- the greater the angular momentum, the great the transfer of momentum to the object (eg. to a ball)
- the further a mass is from the axis: the larger the MOI
Further away from axis:
MOI increases, AV decreases - move/spin slower
Closer to axis:
MOI decreases, AV increases - move/spin quickly (e.g., diving - tuck)
As MOI and Av affect each other, angular momentum is conserved (remains the same)
Simultaneous Force Summation
The use of multiple body parts at the same time to produce force.
e.g., sprint start - when sprinter explosively moves multiple body parts at the same time at the start of race
- sprint start, diving off platform
- explosion of force over a short period of time, producing a faster reaction
Sequential Force Summation
Activation of body parts that are used in sequence to produce force
Includes:
- transferring force from larger muscle groups to begin with to smaller muscle groups at the end.
- transferring momentum from one body part to another when at maximal velocity.
e.g., starting with larger muscle groups of lower body, transfer force to torso, then smaller muscle groups in arms before momentum is transferred to the ball on release - cricket bowl
Newton’s 1st Law
Law of Inertia
“An object with stay at rest or continue to travel in the same direction at a constant velocity unless acted on by an unbalanced force”
- the higher the mass, the greater the inertia, and therefore more force is required to overcome this inertia.
Newton’s 2nd Law
States that:
“The rate of acceleration of a body is proportional to the force applied to it and in the direction in which the force is applied”
- to produce maximal force, mass and acceleration must be at its highest.
- more force has to be applied to a greater mass, more acceleration, therefore the object will move in that direction.
e..g, a soccer kick with greater force, will have greater acceleration, and will travel in the direction it is applied.
Newton’s 3rd Law
“For every action, there is an equal and opposite reaction”
- When one body applies a force against a second body, the second body applies an equal force in the opposite direction on the first.
e.g., basketball hitting backboard on an angle bounces off on an angle with similar force in which it was thrown.
