Linear and Angular Kinetics of Human Movement

What does the law of gravitation state?

All bodies attract each other with a force proportional to their masses and inversely proportional to the square of the distance between them.

Why is it easier to pull than push a heavy object?

Pulling reduces the reaction force by adding an upward component, reducing friction.

How is linear momentum defined?

mass × velocity; a vector quantity.

How is mechanical work defined?

force × displacement in the direction of the force.

How is power calculated?

work ÷ time; measured in watts.

What is moment of inertia?

Resistance to angular acceleration, dependent on mass and its distance from the axis.

What is radius of gyration?

Distance from the axis where mass could be concentrated without changing rotational characteristics.

What are principal moments of inertia?

The body’s moment of inertia values around principal axes.

How is angular momentum calculated?

Moment of Inertia (I) × Angular Velocity (ω).

What factors determine angular momentum?

Mass, mass distribution, and angular velocity.

What does the conservation of angular momentum state?

Angular momentum stays constant without external torque.

Why does a diver tuck?

Decreases moment of inertia → increases angular velocity (conserving angular momentum).

What is angular impulse?

Torque × time; causes a change in angular momentum.

How is torque calculated?

force × moment arm.

What is the kinetic chain concept?

Sequential transfer of angular momentum from larger proximal segments to distal segments (e.g., tennis serve).

Why does bending during landing reduce injury?

Increases time of force application → reduces peak GRF.

How does knee flexion affect moment of inertia during sprinting?

Increases knee flexion → decreases moment of inertia → faster leg swing.

Which contraction performs positive work?

Concentric.