Biomechanics

Angular Kinetics and Gravity

• The center of gravity is the point where the weight of the body can be considered to be acting.
• The center of gravity changes if the body's position is changed.

Angular Momentum and Rotary Motion

• Angular momentum is the quantity of motion that a rotating object possesses.
• The components of angular momentum are mass, velocity, and radius of rotation.
• The rotary equivalent of Newton's 1st law of inertia is that an object at rest will remain at rest, and an object in motion will continue to move in a circular path, unless acted upon by an external torque.

Forces and Motion

• An equal and opposite reaction elsewhere in the body is caused by Newton's 3rd law of motion.
• The work done when a resistance is moved over a certain distance is force × distance.
• Resistance to movement is called friction.
• The desire of an object to continue doing whatever it's doing is called inertia.

Linear Motion and Inertia

• Gravity is a factor that influences linear motion by decelerating the object on the way up and accelerating it on the way down.
• Inertia refers to the tendency of an object to maintain its state of motion.
• Newton's second law of motion is represented by the equation F = ma (force = mass × acceleration).
• The relationship between body mass and muscular force needed is that a larger mass requires a greater muscular force to produce a given acceleration.

Momentum and Impulse

• The formula for momentum is p = mv (momentum = mass × velocity).
• Impulse is the change in momentum of an object.
• The relationship between the area of impact and the force in landing is that a smaller area of impact results in a greater force.

Running and Walking

• The formula for calculating running velocity is v = d/t (velocity = distance ÷ time).
• The stance phase is one of the stages in walking and running.

Angular Velocity and Motion

• Angular velocity describes the rate of change of angular displacement.
• Chapter 5 covers linear motion in sport.

Speed and Velocity

• The difference between speed and velocity is that speed is a scalar quantity, while velocity is a vector quantity.
• Velocity and speed can be the same when the object is moving in a straight line.
• Acceleration/deceleration is the rate of change of velocity.
• A force is needed to hold an object stationary or make it move.

Formulas

• The formula for speed is v = d/t (speed = distance ÷ time).
• The formula for velocity is v = Δx/Δt (velocity = change in displacement ÷ time).
• The formula for acceleration is a = Δv/Δt (acceleration = change in velocity ÷ time).
• The formula for deceleration is a = -Δv/Δt (deceleration = -change in velocity ÷ time).
• Velocity has direction, which speed does not.