Biomechanics Flashcards
Biomechanics
Science that studies living things from a mehcanical perspective, that can help develop and refine human movement.
Quantitative movement analysis
uses numerical data to assess human movement (how fast - stop-watch)
Force
A push or a pull. Can change the shape, move the object or alter movement of the object.
Force =
mass x acceleration (Newtons)
Type of force
friction, gravitational force, drag force and weight
Friction
a force that occurs when two surfaces come in contact with each other. Opposes motion. (curling: smooth ice out, reduces friction, so stone travels faster)
Two types of frictional forces
Gravitational and drag force
Drag force (air and water)
A frictional force when one surface is air or water, that opposes direction of motion of an object (slowing it down).
As speed increases…
drag increases.
Gravitational force
a frictional force of attraction between two objects. On Earth, objects fall downward toward the centre of Earth. (is constant until drag force effects)
Acceleration due to gravity
9.8m/s^2
Weight
the force exerted on the body by gravity.
Weight =
mass x gravity (Newtons)
Mass
amount of matter in an object (kg).
Greater the mass…
greater the inertia.
Inertia
tendency for body to resist/oppose change in its state of motion (what keeps you going) (medicine ball has greater inertia than volleyball)
Momentum
“mass in motion (on the move) “ The quantitiy of motion on the body (force or speed of movement) The greater momentum, harder it is to stop.
Momentum =
mass (kg) x velocity (m/s) (kgm/s)
Two objects with the same mass but different velocities…
( one object should ) increase velocity to increase momentum.
Two objects with the same velocities but different masses
object with greater mass, will have greater momentum (can’t change mass of an object)
A collision between two objects…
both will move in the direction of the object with the greatest momentum.
Conservation of momentum (Mv = mV)
Total momentum before collision = total momentum after collision.
Summation of momentum
Sequential, coordinated movement of each body segment at the same time to generate force. (throwing a tennis ball with wrist, shoulder, trunk will go further than throwing with just your wrist)
BEST summation of momentum
Use as many Body parts as possible, sEquence move the heavier body parts first then the lighter, body parts must be Stable so momentum is not lost and move the next body part when the previous body part has reached maximum velocity.
Impulse
The amount of time at which the force is applied.
The change in momentum of an object. To change momentum, a force must be applied over a period of time
Impulse =
force x time
Impulse example
a softball struck with a large force, the ball is in contact with the bat for a fraction of a second. Compared to, a golf ball rolling along a putting green until it comes to an eventual stop. This is a small force applied over a greater period of time. But both experience a change in momentum.
How can impulse be manipulated?
by increasing or decreasing the velocity of an object. (an increase in time over which the force is applied, will result in a greater impulse being applied and a greater release velcoity of the shot in shot put)
Linear Distance
path travelled from start to finish.
Linear Displacement
change in position of object from start to finish.
Linear Speed
Time taken to cover distance. Speed = distance / time
Linear Velocity
How quickly an object changes it’s position. Velocity = displacement / time
Linear Acceleration
how quickly an object changes it’s rate of motion.
Change in speed/velocity over time.
(eg. start of 100m race has greatest acceleration)
Newton’s 1st law of motion (intertia)
A body will remain at rest or in constant motion unless acted upon by an external force (F=ma)
(eg. soccer ball will stay still, until kicked)
Newton’s 2nd law of motion (acceleration)
A force applied will produce a change in motion (acceleration) in the direction of the applied force that is directly proportional to the size of the force. (football kicked harder, with greater force, will go further than a little tap, with less force)
Newton’s 3rd law of motion (action-reaction)
For every action, there is an equal and opposite reaction. (running on an athletics track is faster than on sand, because force is pushed back to you from the ground, whereas force moves the sand, reducing force generated back into athlete to maintain speed)
General Motion
A combination of linear and angular motion.
Linear Motion
Movement of a body or object in the same direction and same speed, along a straight or curved path.
Angular motion
Movement of body around a fixed point or central axis (in a circular motion)
Torque
a rotational force (push or pull) that makes an object rotate.
Torque = force x lever
Eccentric force
A force that does not act through an objects’ centre of gravity. Torque is caused by an eccentric force.
Angular Distance
sum of all angular changes measured in degrees.
Angular Displacement
difference between initial and final angular position measured in degrees.
Angular Speed
Rate of change of angular distance.
angular distance / time
Angular Velocity
Rate of change of angular displacement.
angular displacement / time
Angular Acceleration
Rate of change of angular velocity
change of angualr speed/velocity / time
Newton’s 1st law of angular motion (inertia)
The angular momentum of a body remains constant unless acted upon by an external torque.
Newton’s 2nd law of angular motion (force and acceleraction)
A torque applied to an object will produce a change in angular motion in the direction of the applied torque that isdirectly proportional to the size of the torque.
Newton’s 3rd law of angular motion (action-reaction)
For every torque, there is an equal and opposite reaction.
Moment of inertia
the resistance to an object’s change in state of angular motion. (greater MOI longer heavier bat, harder to swing, greater velocity at end of bat transferred into greater velocity in the ball)
Moment of intertia =
mass x radius^2
Angular momentum
the amount of angular motion by a body
Moment of inertia x angular velocity
Projectile motion
A projectile is an object or body that travels through air. Affected by: angle, height and speed of release.
Angle of release
The angle at which the projectile is projected into the air; optimal angle of release will result in greater distance covered by the projectile.
Speed of release
the speed at which the projectile is projected into the air; will affect horizontal and vertical distance of projectile.
Height of release
the difference between height of release and landing height of projectile; height of release will affect optimal angle of release
Equilibrium
when all forces and torques are balanced.
Static equilibrium
a body that is not moving or rotating. (The sum of all vertical, horizontal forces and torques acting on body is zero)
Dynamic equilibrium
a body is moving with constant velocity and no change in speed or direction.
Balance
the ability to control equilibrium.
Increased stability is harder to unbalance.
Musculoskeletal strength and flexibility contribute to good balance.
Stability
the resistance to the disruption of equilibrium.
Factors affecting stability
base of support, centre of gravity, body mass, friction
Base of support
the area bound by outside edges of the body part in contact with the support surface.
Increased BoS - increases stability.
Centre of gravity
the point at which your weight is balanced regardless of your body position. lowering centre of gravity – increases stability.
Line of gravity
imaginary line that passes through centre of gravity. When line of gravity is through BoS, increase stability
Body Mass
the greater the mass of an object the harder it is to move and disrupt equilibrium. (F=ma)
Friction
increased friction increases stability.
Components of a lever
axis, force and resistance
Axis
the turning point of the lever
Force (lever)
the point where the force is applied
Resistance
the weight of whatever the person is trying to move.
First class lever
axis is between force and resistance. Muscles provide the force in human body.
Second class lever
resistance is between force and axis. Only one in human body. Levers generate greater force to move large resistance
Third class lever
force is between resistance and axis. Most common in human body.
Increases range of motion and speed of lever.
Mechanical Advantage
force arm/resistance arm
Force arm
distance between force and axis
Resistance arm
distance between resistance and axis
Mechanical advantage >1
force arm is greater than resistance arm. Less effort to move resistance
Mechanical advantage <1
resistance arm is greater than force arm. Increased range of motion and increased angular speed.
All second class levers have …
mechanical advantage (>1) but greater weight can be moved with less effort.
All third class levers have…
no mechanical advantage (<1) but increased range of motion of the lever.
BEST summation of momentum
