PK6: CH5 Torques and Moments of Force

Torque

turning effect produced by a force (either angular or rotary force)

What determines Vector size and direction?

Size and Direction

True or False: Clockwise is positive(+) and counterclockwise is negative (-)

False, clockwise is negative (-) and counterclockwise is positive (+)

What is a Centric Force? And what kind of change of motion happens?

an external force directed Through an objects center of gravity

• force is being pushed in the center

• change in Linear Motion

What is Eccentric Force? and What change in Motion?

It is an external force NOT directed through the center of an objects

• Applies force either Top or Bottom/ Up or down

• changes in either Linear or Angular motion

What is a Force Couple? and Change in Motion?

Pair of courses are equal in size, but opposite in direction

• Apply forces to One corner and then the opposite

• causes change ONLY in the angular motion

What determines the magnitude or size of torque?

Size of Force & Speed

True or False: The more distance = easier to rotate

True, think of opening a door and where the handles are hinges are

Moment Arm

perpendicular distance from the forces line of action to the axis of rotation

Equation for Torque

T= F x r in Newton Meters (Nm)

r= moment arm

Does r increase if F decrease or vise versa?

YES!!!! R does INCREASE if F decreases

What does Muscular Torque do?

our muscles create torque that move our limbs and joints

Agonist Muscle

Contracts to create a movement

Antagonist Muscle

relaxes and lengthens to allow movement to happen

True or False: Tension in the antagonist muscle controls the velocity of the movement and enhances stability

True !

Line of action of a muscle force is along a line joining attachments usually indicated by….

the direction of its tendon

When is a muscle’s moment arm is largest when the angle of the pull is?

90 degrees

For a muscle to produce a constant joint torque it must…..

produce more Force as its moment arm decreases

T=increase F x decrease r

Define Center of Gravity (COG)

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

is COG real?

its an imaginary point in space

what are the three things that COG depends on to be balanced

1. all linear forces acting on the body must be balanced

2. all rotary forces (torque) must be balanced

3. sum of all forces acting on the body must be

Do woman have a slightly higher COG?

No, they have a slightly lower COg due to the wider hips and more narrow shoulders

Men vs Women COG?

Women COG: 55% of height from the ground

Male COG: 57% of height from the ground

True or False: Can COG be outside the body?

Yes, like a donut or a figure skater

Stability

an objects ability to return to equilibrium or its original position after it had been displaced

Stable Equilibrium

when an object is placed in an effort to disturb it requires the COG to be raised

ie: brick on its side

Unequal Equilibrium

exists whe it takes only a slight (force) push to destroy it

ie: sprinters at the start of the race or getting pushed back or wrestling stance

True or False: Lowering height of COG will decrease stability

False, it increase stability

ie: think of getting big in wrestling

True or False: the greater the mass, the greater the stability

true it is easier to move a 120lb person in comparison to 250 lbs

What is Base of Support (BOS)

It is a image that shows a stance that points out each point of support

ie: think of sports like swimmers and wrestlers