Biomechanics Flashcards
Define Force and how its measured?
- An influence that may cause a body to alter its state of motion.
- Measured in newtons
Define concentric force
-Force applied to produce linear motion
Define eccentric force
- Force applied to produce angular motion
- rotational force
- occurs when force is applied away from the COG of an object.
- results in angular velocity
What is the conservation of momentum principle?
-The conservation of momentum principle states that when an object is moving it has momentum and as long as no force is applied to speed the object up or slow it down its momentum is said to be conserved.
So in basic terms when a collision occurs the total momentum before the collision should be equal to the momentum after the collision.
What is newtons first law?
- An object at rest will remain at rest and a moving object will continue moving unless acted upon by an unbalanced (external)force.
- Known as inertia
- Greater mass = greater inertia
What is newtons second law?
- The rate of change of acceleration to a body is proportional to the force applied to it and inversely proportional to the mass of the object.
- Represented by F=ma
What is newtons third law?
- For every action there is an equal and opposite reaction.
- Forces work in pairs opposing one another.
What is momentum?
- The momentum of an object is equal to its mass multiplied by its velocity.
- P= m x V
- P=momentum
Define impulse
- Impulse is the change in momentum.
Impulse = Force x time
- Area under line in graph is the impulse
State the relationship of impulse and creating force and in turn velocity.
- The greater the impulse the greater the greater the change in momentum and therefore the greater the force produced and therefore the greater the velocity of the object.
State the relationship of impulse when absorbing force.
- The greater the impulse the greater the change in momentum and therefore the lower the peak force of the object.
- Lower peak force = less risk of injury
Why in sports do people use a ‘follow through’?
- This is because using a follow through will increase the time of contact with the ball increasing the change in momentum (impulse) and thus increasing the velocity of the object allowing it to travel a further distance.
- More momentum = more velocity
- Also prevents object from deaccelerating before release
Define co-efficient of restitution.
- A value representing the ratio of velocity after an impact compared with the velocity before the impact.
COR = 1 = collides elastically (linear momentum fully conserved ) perfect
COR= 1< - imperfect elastic Collison (normal)
COR= 0 - Object does not bounce at all (linear momentum not conserved at all)
What are the 3 main factors that effect COR?
- The materials of the intersecting bodies, e.g. new tennis ball have higher COR then old and different surfaces clay vs grass
- The velocity of the Collison - Higher velocities reduce COR because greater compression of ball thus greater difference between the velocity before and after
- The temperature of the materials involved - Higher temperature = Higher COR
What are the three main parts of a lever?
- force/effort
- fulcrum/pivot
- resistance/ load
What is the resistance arm of a lever?
- The distance between the resistance and the fulcrum
What is the force arm of a lever?
- The distance between the force and the fulcrum.
What is a first class lever?
- A lever which has the fulcrum between the force and the resistance
- when fulcrum is in middle balanced movements are made, when fulcrum is closer to force speed and range of motion is optimal, when fulcrum is close to resistance optimal force is produced
What is a second class lever?
- when the load is between the fulcrum and the force.
- Produce forceful movements since large resistance can be moved by relatively small force. e.g. wheel barrow
What is a third class lever?
- A lever which has the force located between the fulcrum and the load.
- effective at producing speed due to their large range of motion
- Large amount of force required to move small resistance
- Most common type of lever in the body, e.g. Bicep
What does mechanical advantage mean?
- If the force provided is multiplied by the lever system to produce a greater output.
- Levers with a larger force arm than resistance arm will offer a mechanical advantage
- Second class levers always offer mechanical advantage.
Speed (levers)
- Third class levers are optimal for fast actions as they have relatively larger resistance arm than force arm.
- Force arm move over small distance = move resistance arm larger distance
What are the factors effecting lever use?
- Length of lever = greater velocity and momentum but less accuracy (e.g. golf)
- Inertia of lever - Heavier the lever the harder it is to rotate
- Amount of force -The amount of force an athlete is able to generate via their muscles determines the length of the lever the athlete should use.
What is a rotational force?
- A rotational force is called a eccentric force and occurs when force is applied away from the COG of an object
- eccentric force develops angular velocity