Biomechanical Principles Flashcards
Define force ?
A push or pull that alters a state of motion of a body.
A force can cause a moving body/object to :
1) Change direction - return a tennis shot
2) Accelerate - sprint starts
3) Decelerate - ski slope
4) Change shape - trampoline springs
What is the triangle for Force, Mass and Acceleration ?
Force at the top with mass and acceleration on the bottom
Force = mass x acceleration
Mass = force / acceleration
Acceleration = force / mass
What are the units used for force, mass and acceleration ?
Force - newtons (N)
Mass - kilograms (Kg)
Acceleration - meters per second squared (M/S squared)
What are the two types of forces and provide examples of ?
Internal force - produced by concentric muscle contraction
External force - gravity, air resistance, friction, reaction force and water resistance
What are the three types of motion ?
Linear motion - movement in a straight line (100m sprinter)
Angular motion - movement in a circular path around a point or axis (gymnast on bars)
General motion - mixture of both (swimmer moving forward and arms rotating in stroke)
Explain Newtons 1st law of motion with sporting examples ?
1) law of inertia
An object will stay at rest or keep moving at a constant velocity unless acted on by external force.
A winger will continue to run in a straight line at a constant velocity unless opposition comes and tackles them.
Define inertia ?
Inertia - the reluctance of an object to change its state of motion. The mass of an object has the greater its inertia.
Explain Newtons 2nd law and provide sporting examples ?
2) law of acceleration
The acceleration of an object depends on the force applied and the objects mass (f=mxa)
Force and acceleration are directionally proportional (if a force increases then the acceleration will increase
Rugby player during a penalty, applies a force to a ball, it will move in the direction that this force is applied.
Explain Newtons 3rd law and provide sporting examples?
3) Law of action and reaction
For every action, there is an equal and opposite reaction (ground force reaction).
When one object exerts a force on another, the second object simultaneously exerts an equal and opposite force back on the first object
Sprinter pushing out of the starting blocks in a 100m sprint.
What’s the formula triangle for force, mass, acceleration ?
Force
Mass. Acceleration
What’s the formula triangle for speed, distance and time ?
Distance
Speed. Time
Define momentum ?
The quantity of motion. The product of mass x velocity
Define velocity ?
The speed something is moving in a given direction.
Define impulse ?
The product of force and time it takes to apply the force.
Impulse = change in momentum
Define net impulse ?
Net impulse is the overall change in momentum of an object.
Explain positive impulse ?
This occurs when force is applied in the same direction as the motion of an object, increasing its velocity.
Explain negative impulse ?
This occurs when force is applied in the opposite reaction to the motion of an object - decreasing its velocity, slowing it down
How can a performer increase impulse ?
1) increasing the force applied
2) increasing the time this force is applied (extended duration)
3) combining both force and time (apply a greater force over a longer time)
Define stability ?
The ability of a body to return to equilibrium after being displaced.
Define centre of mass ?
The point at which the body is balanced in all directions.
Define balance ?
The ability to stay stable and not fall when standing still or moving.
Explain base of support ?
An object with a larger base of support can keep their centre of mass over the base of support and is then more stable.
What factors affect the stability with sporting example ?
1) Mass of an object - the greater the mass, the more stable an object is because it has greater inertia.
A sumo wrestler is more stable than a lightweight boxer because they have more mass.
2) size of base of support - larger BOS support increase stability as there is a bigger area to balance.
A rugby player standing with feet width apart is more stable than one standing close together.
3) height of centre of mass - lower COM improves stability reduces chance of falling.
A skier bending their knees stays more stable than standing upright.
4) points of contact - more points of contact provide greater stability as weight is distributed.
A gymnast on all fours is more stable than one balancing on one.
What the three parts of a lever system ?
Fulcrum - the fixed point or pivot
Load - the point where resistance is from
Effort - the point where force/effort is applied
What are the two main functions of levers?
1) increase the speed and range of motion
2) to generate maximal force
Describe first class levers ?
- fulcrum is in the middle
- joint at the neck
- effort and load point down
- heading in football (tricep extension)
Describe second class levers ?
- load is in the middle
- joint at the ankle
- effort is up load is down
- long jump take off (calf raises)
Describe third class levers ?
- effort is in the middle
- most joints (knee,elbow,shoulder,hip)
- free kick, boxing uppercut (bicep curl)
What is the mechanical advantage/disadvantage for second class?
Adv - longer effort arm therefore can lift heavier loads more efficiently.
Dis - can’t create fast speed and limited range of motion.
What is the mechanical advantage/disadvantage for third class?
Adv - longer load arm which allows for greater range of motion and faster speeds.
Dis - requires more effort to move a heavy load
