Flashcards in Chapter 7 - Biomechanics Deck (99)
what is the point about which movement occurs?
the axis of rotation
all joints are what type of motions?
a combination of linear and angular motion
what does general motion include?
most athletic and many everyday activities
causes of motion
the only cause of motion of the human body is the application of an external force
any action, a push or pull, which tends to cause an object to change its state of motion by experiencing an acceleration
occurs when an object is not accelerating
is caused by forces which act through a body's centre of mass
caused by forces that do not go through the centre of mass
centre of mass
located at the balance point of a body; a point found in or about a body where the mass could be concentrated
where is the centre of mass generally?
generally 15cm (approx. 6inches) above the symphysis pubis, or approx. 55% of standing height in females and 57% in males
does the centre of mass have to be inside the body?
a measure of inertia a constant what object is made up of
what is mass measured in?
measure of the force of gravity
what is weight measured in?
what makes the weight vary?
varies directly with the magnitude of the acceleration due to gravity (9.8m/s2)
Weight = _____ x ______
mass x gravity
any airborne object is a projectile, including the human body
the path that the centre of mass of a projectile follows
what is the parabolic path followed determined as?
determined only as a function of the projectiles takeoff velocity
what are the objectives of the projectile motion (what do you want the object to do)?
height - max vertical distance
range - max horizontal distance
what is the optimum trajectory for distance?
what is the first principle?
stability increases when there is...?
- a lower centre of gravity
- an increase in the base of support
- the line of gravity is close to the centre of the base of support
- mass increases
what is principle #2?
how is maximum force achieved
by the use of all the joints that can be applied simultaneously
more joints = more ______ = more _______
more joints = more muscles = more force
what is the third principle?