Lecture 4

To increase stability (2)

1) decrease toppling force and/or the moment arm of the toppling force 2) increase weight of the object and/or moment arm of the object

3 things that affect the stability of an object

1) the height of the center of gravity 2) the size of the base of support 3) the weight of an object

Torque (2)

1) the turning effect created by a force 2) also called a moment of force

In anatomical position, the height of your center of gravity is ___ to ___ of your standing height.

55%, 57%

T/F: If some of the elemental parts of an oject move or change position, the center of the gravity of the object does not move.

False, moves as well, although not as far

T/F: Max vertical distance is achieved by putting the largest amount of mass overhead.

False, smallest

Jumping with one arm up, both arms up, or arms up and legs tucked, which will give you the highest jump.

Just one arm up

Units of torque

Nm

T/F: During a leap, the jumper's head stays at the sam level but the center of gravity follows a parabolic path.

True

T/F: For each limb movement, the center of gravity of the entire body shifts slightly in the direction of that movement.

True

T/F: If an elemental part is removed the center of gravity moves away from the point of removal, while if mass is added the center of gravity moves toward the location of added mass.

True

T/F: In the human body, the center of gravity lies on the midline left to right and front to back and between 55% to 57% of a person's height above the ground when standing in anatomical position.

True

T/F: The center of gravity is the point at which the entire mass or weight of the body may assumed to be concentrated.

True

T/F: The motion of your limbs when you were in the air could not alter the motion of your center of gravity because they are not pushing or pulling against anything external to your body.

True

T/F: Torque is a vector quantity.

True

The center of gravity is the point of ________.

balance

"Raising" your center of gravity is relative to your _____ not the ______.

body, ground

For our purposes, center of gravity is the same as _____ __ ___.

center, of, mass

The book is most stable when it is lying ____ on the table. This is the orientation tha tputs its center of gravity and the _______ position.

flat, lowest

Raising on leg out in front of you will move your center of gravity ______ and ______ farther than will raising one arm out in front of you. This is because legs have more ___.

forward, upward, mass

Infants have higher centers of gravity due to their ____ _____.

large, heads

Women have a ____ center of gravity compared to men, this is due their ____ pelvic girdles.

lower, larger

Torque is equal to the _________ of the force times the _________ distance between the line of action of the ____ and the axis of ________ about which the torque is being measured.

magnitude, perpendicular, force, rotation

The path that your center of gravity followed was __ _____ by your limb actions, but these actions caused the motions or your other limbs and trunk to _____. Lifting your arms caused something else to move _________ in order for your center of gravity to continue moving in a ________ path. When you raised your arms and legs, your head and trunk got lower to __________ for this movement.

not, changed, change, downward, parabolic, compensate

Stability

the capacity of an object to return to equilibrium or to its original position after being displaced

Center of Gravity

the point in a body or system around which its mass or weight is evenly distributed or balanced and through which the force of gravity acts

Center of mass

the point in a body or system of bodies at which the entire mass my be assumed to be concetrated