Biomechanical Principles Flashcards
define force
a push or pull that alters or tends to alter the state of motion of a body
what can a force cause a body that is at rest do?
cause it to move
what can a force cause a moving body to do? (4)
- change direction
- accelerate
- decelerate
- change the object’s shape
the equation for force:
force = mass x acceleration
“internal forces are generally produced by _______________ muscle contraction”
concentric
“external forces act on an object or structure from the ____________ ; they generally come from the _________________”
outside
environment
list the five external forces
- gravity
- friction
- air resistance
- applied force
- reaction force
what is gravity?
provide a sporting example wherein gravity is in significant effect
the force pulling objects towards the earth
example
a high jumper falling back to the ground
what is friction?
provide a sporting example wherein friction is in significant effect
the force resisting motion between two surfaces
example
a sprinter pushing off the track
what is air resistance?
provide a sporting example wherein air resistance is in significant effect
the force acting against motion through the air
example
a cyclist experiencing a drag
what is applied force?
provide a sporting example wherein applied force is in significant effect
a force exerted by a person or object
example
a footballer kicking the ball
what is reaction force?
provide a sporting example wherein reaction force is in significant effect
the force exerted by a surface supporting an object
example
the ground pushing back on a gymnast’s hands during a handstand
define linear motion (2)
- refers to movement in a straight line, wherein an object moves along a path in one direction
- all parts of the object travel the same distance in the same amount of time
define angular motion (2)
- movement around a fixed point or axis; i.e. rotational
- different parts of the body may travel different distances but all rotate around the same axis
define general motion (2)
- a combination of linear and angular motion
- one part of the body may move linearly whilst other points rotate around an axis
there are three laws of motion, according to isaac newton.
what are each of them known as?
newton’s 1st law
law of inertia
newton’s 2nd law
law of acceleration
newtons 3rd law
law of action and reaction
define inertia
the reluctance of an object to change its state of motion
or
the tendency of an object to remain unchanged
law of inertia explains that…
provide an example wherein the law of inertia is shown within sport
an object will remain at rest or moving at a constant velocity unless acted upon by an external force
in a penalty, the football will remain stationary unless an individual kicks it or the wind happens to act upon it
law of acceleration explains that… (3)
the force acting on an object is equal to the mass of that object multiplied by its acceleration
- the greater the force, the more the object accelerates
- the larger the mass, the harder it is to accelerate
law of action and reaction explains that… (2)
provide an example wherein the law of action and reaction is shown in sport
- for every action, there is an equal and opposite reaction
- when two objects interact, the force exerted on one another is of equal magnitude but different direction
a sprinter pushing against the blocks
the equation for speed:
speed = distance ÷ time
define momentum
the quantity of motion; this is a product of mass and velocity
allows us to understand how mass and velocity influence the movement of athletes and objects
how can momentum be increased in sport, for example?
using a heavier mass
heavier bat in cricket
heavier club in golf
increased velocity
running faster in football
the equation for momentum:
momentum = mass x velocity
define impulse
a change in momentum
how force and time can cause the athlete to start moving or change direction
the equation for impulse:
impulse = force x time
“impulse is represented by…”
the area under a force-time graph
define positive impulse
provide a sporting example
when force is applied in the same direction as the motion of an object, increasing its velocity
a sprinter pushing off the starting blocks; the force applied in the forward direction
define negative impulse
provide an example
when force is applied in the opposite direction as the motion of an object, decreasing its velocity
a long jumper landing in the sand experiences a braking force from the ground
define net impulse
how is it calculated?
the overall change in momentum of an object; it takes into account both positive and negative impulses
subtracting the total negative impulse from the total positive impulse
so how does impulse change momentum in sport? (2)
increasing momentum
athletes aim to generate positive impulse to increase momentum
decreasing momentum
athletes also use negative impulse to decrease their momentum
what are the three ways in which a performer can increase impulse? (3)
- increasing the force applied
- increasing the time the force is applied for (by utilising a follow through)
- applying a greater force for a longer time
define stability
the ability of the body or an object to return to equilibrium after being displaced
define the centre of mass/gravity
the point at which the body is balanced in all directions
define the line of gravity
an imaginary line that passes vertically from the centre of mass/gravity to the ground below an object
define state of equilibrium
where a system remains unchanged and can return to its original state after a disturbance
what are the four factors that affect stability?
- the mass of an object
- the size of the base of support
- height of the centre of mass
- points of contact
how does mass of the object affect stability?
the greater the mass of the object, the more stable it is
THIS IS BECAUSE, a larger mass generates a greater force acting downwards due to gravity; increases inertia
how does the size of the base of support affect stability?
a larger base of support increases stability
THIS IS BECAUSE, the wider the area for the centre of mass to remain within, the more reduced chance of toppling over
how does the height of the centre of mass affect stability?
a lower centre of mass increases stability
THIS IS BECAUSE, the body’s weight is distributed closer to the base of support and so this makes it harder for external forces to tip the body over
how do the points of contact affect stability? (2)
- more points of contact with the ground increases stability
THIS IS BECAUSE, weight is distributed more efficiently
- the greater the size of the points of contact increases stability
THIS IS BECAUSE, there is a greater surface area in contact with the object and therefore greater friction keeping them in place
