1.3a biomechanical principles Flashcards
what is newtons first law?
-Inertia
a body remains in a state of rest or uniform velocity unless acted upon by an external force
eg pass in rugby - ball continues in a state of rest unless acted upon by an external force (produced by arms, wrists, hands)
what is newtons second law?
-acceration
the acceleration of a body is proportional to the force causing it, and the acceleration takes place in the direction in which the force acts
eg golf tee off - the more power the ball is struck with = how quickly it will accelerate and the angle/direction it is struck will determine the direction it will travel
F=MxA
what is newtons third law?
-Reaction
for every action there is an equal and opposite reaction
eg sprint start - sprinters feet push force down onto the ground and the ground pushes an equal force back
vertical forces
weight (down)
reaction (up)
horizontal forces
friction (in direction)
air resistance (opposite direction)
what is net force
the sum of all forces acting on a body
internal forces
generated by a msk contraction
eg drive out of start blocks
external forces
comes from outside the body and acts upon it
eg w, r, f, and ar
what are balanced forces
forces equal in size that have no movement
what are unbalanced forces
one force is greater than another and there is movement
weight
gravitational pull that the earth exerts on a body
-acts down from COM
reaction
equal and opposite force exerted y a body in response to the action force placed upon it (N)
friction
force that opposes the motion of two surfaces in contact (N)
what factors affect friction
-roughness of ground surface
-roughness of contact surface
-temperature
-size of normal reaction
air resistance
force that opposes the motion of a body travelling through the air (N)
what factors affect air resistance
-velocity
-shape
-frontal cross sectional area
-smoothness of surface
what is force
a push or pull that alters the state of motion of a body
force calculation
force (N) = mass (kg) x acceleration (m/s2)
what is momentum
the quantity of motion possessed by a moving body
momentum calaulation
momentum (kgm/s) = mass (kg) x velocity (m/s)
what is acceleration
the rate of change in velocity
acceleration calculation
acceleration (m/s2) = (final velocity - initital velocity (m/s)) / time taken (s)
weight calculation
weight (N) = mass (kg) x acceleration due to gravity (10 ms2)
what to do if there is more than one point of contact
eg handstand
reaction force from each hand has to be half of the weight arrow
W=R1+R2
centre of mass
the point at which the body is balanced in all direction
what affects com
how the body is positioned
eg arms up
if they are holding something
eg bar above head
fosbury flop
take off
-com raised with arms and stays outside body by arching
in air
-com under bar while jumper passes over allowing greater height
what factors affect stability
centre of mass
-lower com, greater stability
base of support
-greater size bos, greater stability
line of gravity
-central log to bos, greater stability
mass of body
-greater mob, greater inertia and stability
