biomechanics p2

Question 1

Angular motion

Answer 1

Movement of a body or part of a body in a circular path about an axis of rotation

Question 2

Eccentric force

Answer 2

A force applied outside the centre of mass, resulting in angular motion

Question 3

Torque

Answer 3

A measure of the turning (rotational or eccentric) force applied to a body

Question 4

Angular velocity

Answer 4

The rate of change in angular displacement measured in radians per second (rate of spin)

Question 5

Moment of inertia

Answer 5

The resistance of a body to change its state of angular motion or rotation

Question 6

Angular momentum

Answer 6

The quantity of angular motion possessed by a body

Question 7

Conservation of angular momentum

Answer 7

Angular momentum is a conserved quantity which remains constant unless an external force or torque is applied

Question 8

Angular analogue of Newton’s first law of motion

Answer 8

a rotating body will continue to turn about its axis of rotation with constant angular momentum unless acted upon by an eccentric force or external torque

Question 9

equation for angular velocity

Answer 9

angular velocity = angular displacement/time taken

Question 10

equation for moment of inertia

Answer 10

sum of(mass x distribution of the mass from the axis of rotation squared)

Question 11

two factors that affect the moment of inertia are what?

Answer 11

mass and distribution of mass.

Question 12

explain how moment of inertia has a direct effect on angular velocity

Answer 12

-if moment of inertia is high, resistance to rotation is also high, therefore angular velocity is low: the rate of spin is low.
-if moment of inertia is low, resistance to rotation is also low, therefore angular velocity is high: the rate of spin is fast.

Question 13

practical example in depth of angular momentum remains Constanta bout the longitudinal axis throughout flight when performing a triple Axel jump in ice skating

Answer 13

1. the ice skater starts rotation about longitudinal axis.
2. their distribution of mass is away from the longitudinal axis as their arms and one leg are held away from the midline. the moment of inertia is high and therefore angular velocity is low. they go into the jump rotating slowly and with control.
3. picture B shows how during flight the ice skater distributes their mass close to the longitudinal axis as they tuck in their arms and legs. the moment of inertia is decreases and therefore angular velocity is increased, they spin quickly allowing several rotations in the time available in the air.
4. picture c shows how in preparation to land the ice skater distributed their mass away from the longitudinal axis, opening out the arms and one leg. the moment of inertia is raised and angular velocity reduced. they decrease their rate of spin, increasing their control for landing and preventing over rotation.
5. as they land the ice applies an external torque to remove the conceived quantity if angular momentum maintained throughout the jump to move away smoothly.