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3.2 - lever systems and stability - Coggle Diagram
3.2 - lever systems and stability
centre of mass
the point at which a body is balanced in all directions; the point from which weight appears to act
the position of centre of mass can be moved by altering body shape and can lie outside the body
Example = Fosbury Flop high jump technique
stability
the ability of a body to resist motion and remain at rest
the ability of a body to withstand a force applied and return to its original position without damage
factors effecting:
mass of body = the greater the mass of the body, the greater its inertia, therefore the greater the stability
height of the CoM = the lower the CoM, the greater the stability
base of support = the greater the size of the base of support the greater the stability
line of gravity = an imaginary line which extends from the CoM downwards to the floor, the more central the line to the base the greater the stability
maximising stability
example - sprinter in the blocks has maximum stability because they are in a crouched position giving a low CoM and the base of support is large
minimising stability
example - when they are set, they lift their hips, raising their CoM and leans forward shifting the line of gravity meaning stability is reduced ready for movement
Lever systems
to generate muscular effort to overcome a given load
to increase the speed of a given movement
1st class
E-F-L = fulcrum in the middle
Example = extension of the neck when preparing to head a football
2nd class
E-L-F = load is in the middle
Example = ball of the foot in the take-off phase of a high-jump
3rd class
L-E-F = effort is in the middle
Example = flexion of the elbow during a bicep curl
efficiency of the lever system
effort arm = the distance from the fulcrum to the effort
load arm = the distance from the load to the fulcrum
mechanical advantage =
second class lever system where the effort arm is greater than the load arm
large load can be moved by a relatively small effort
mechanical disadvantage =
third class lever system where the load arm is greater than the effort arm
a large effort is required to move a relatively small load
lever = bone
fulcrum = joint
effort = muscular force
load = weight or resistance