week 10 biomechanics Flashcards
exam 2, revision
What is the relationship between linear and angular velocity?
The linear distance travelled is proportional to angular displacement and radius. The further away from the joint, the larger the linear distance traveled.
Tendons are often attached very close to joints; thus, they just need to cover a very small angular displacement to produce a large linear distance at the end of the segment.
How does linear velocity relate to angular velocity?
Linear (tangential) velocity at the end of a rotating segment depends on angular velocity of the segment and distance from the axis of rotation (radius).
vT = r ω
What is moment of inertia?
Moment of inertia is the resistance of a body to changes in its angular motion, depending on mass and how mass is distributed with respect to the axis of rotation.
I = m r²
What factors affect moment of inertia?
The more massive a body is, the more difficult it is to start or stop rotating it. The more mass concentrated further away from the axis, the higher the moment of inertia.
What are the teaching implications for children’s equipment?
Children need equipment with inertial characteristics enabling them to develop correct movement patterns. Often, the equipment they are given has inappropriately large inertia.
How does increased knee flexion affect sprinting?
Increased knee flexion of the recovering leg reduces moment of inertia around the transverse axis of rotation, making the swing-through faster.
What is linear momentum?
Linear momentum is the quantity of motion possessed by a body, calculated as Momentum = Mass x Velocity.
L = mv
What is angular momentum?
Angular momentum is the quantity of angular motion possessed by a body, calculated as Angular momentum = Moment of Inertia x Angular Velocity.
H = I * ω
What does Newton’s 1st Law of Angular Motion state?
If no external torques are applied, then the body’s angular momentum remains unchanged.
What is the relationship between angular momentum and external torques?
Angular momentum can change by redistributing mass around the axis of rotation, even if no external torques are applied.
What does Newton’s 2nd Law of Angular Motion state?
The rate of change in angular momentum is proportional to the torque acting on it and in the direction that the torque acts.
T = I α
What does Newton’s 3rd Law of Angular Motion state?
For every torque exerted by one body on another, there is an equal and opposite torque exerted by the second body on the first.
How can angular momentum be transferred?
Angular motion of body parts can change by transferring angular momentum from one body part to another.
Why do long jumpers use the hitch-kick technique?
Long jumpers use this technique to control forward rotation at take-off and manage angular momentum through arm and leg rotations.
What is the angular impulse-momentum relationship?
Angular impulse (T.t) equals the change in angular momentum, allowing for increases in angular momentum through applied force, moment arm, or time.
How does a diver generate sufficient rotation for a backward somersault?
A diver must apply large forces to the springboard for as long as possible, using a large moment arm to generate sufficient rotation.
