Biomechanical principles of Equilibrium

Question 1

Equilibrium

Answer 1

Object is said to be in a state of equilibrium when there are no unbalanced forces or torques acting on an object.

Static equilibrium: no movement or rotation

Dynamic equilibrium: the object or body is moving with a constant velocity
no change in speed or direction

Balance:
the ability to control equilbrium

Question 2

Stability (and factors that affect stability )

Answer 2

the resitance to the disruption equilibrium
in sports we increase stability (wrestling) and at other times, we want to decrease (blocks in swimming)

Factors that affect stability:
- base of support
- centre gravity
- line of gravity
- body mass
- friction between the body and contacting surfaces

Question 3

Base of support

Answer 3

BOS is the area bound by the outside edges of the body parts in contact with the supporting surface.
the greater the bos, the greater the stability of an object
bos could be increased by spreading feet further apart, crouching over and placing your hands on the ground, or leaning against another object.

Question 4

Centre of gravity

Answer 4

cog is the point around which the weight is balanced

cog can be manipulated by moving your body into different positions

the lower your cog the greater stability you have

cog can also fall outside (leaning towards toes, blocks)

when mass distribution of the object is not constant, the centre of gravity will shift in the direction of greater mass e.g baseball bat compared to shot up.

Question 5

Line of gravity

Answer 5

gravity acts on a body through the COG. the direction in which the gravity acts is called the line of gravity.
when the line of gravity is in the centre of the BOS, stability is the greatest.
as the line of gravity moves to the edge of BOS the athlete becomes more unstable.

Question 6

Body mass

Answer 6

the greater the mass of the body, the greater the stability
beneficial in sports like wrestling, where greater stability is beneficial

disadvantage in gymnastics, where quick changes in stability is required

Question 7

Friction

Answer 7

increased friction can increase stability
e.g surfboard wax increases friction between the surfer’s feet and board

Question 8

Levers (what are they made up of and how the body creates movement through them)

Answer 8

“a lever is a simple machine that consists of a rigid bar, an axis to rotate around, a force and a resistance.

made up of:
- an axis (or pivot point)
- a resitance (weight/load to be moved)
- a force (or effort)

Can create movement through:
- the bone is the rigid bar
- the joint is the axis
- the muscle is the force
- the body weight or an object that’s being held is the resistance

Question 9

first class levers

Answer 9

the axis is the middle of the resistance and force (FAR)

beneficial for producing force or speed (depending on distance of force and resistance from axis)

1 or more than 1 = mechancial advantage

Question 10

Second-class levers

Answer 10

the resistance is in the middle of the force and axis
very few e.g in human body
beneficial for increasing force

calf raises muscle (resistance is the heel axis is ball of foot, force is muscle

e.g like the wheelbarrow- beneficial for increasing force (more than 1 mechanical axis)
longer the force arm = greater force

Question 11

3rd class lever

Answer 11

force is in the middle (a foot race)

most common type of lever in human body/sports

resistance most commonly at the end (gold club, bat)

axis = joint

force applied in between via insertion of the msucle across the joint (force= where muscle attaches)

mechanical advantage = less than one (more speed and greater range of motion)