biomechanics yr 2

Question 1

linear motion

Answer 1

movement of a body in a straight or curved line, where all parts move the same distance in the same direction over the same time

Question 2

direct force

Answer 2

a force applied through the COM resulting in linear motion

Question 3

5 linear motion descriptors

Answer 3

• distance
  -displacement
  -speed
  -velocity
  -acceleration / declaration

Question 4

speed

Answer 4

the rate of change in distance

Question 5

Angular motion

Answer 5

movement of a body or part of a body in a circular path about man axis of rotation

Question 6

how does angular motion occur

Answer 6

from an eccentric force being applied to the body known as torque

Question 7

longitudinal axis

Answer 7

runs from head to toe through the COM
e.g a flat spin of ice or full turn in trampolining

Question 8

Transverse axis

Answer 8

runs from left to right through the COM.
e.g somersault

Question 9

frontal axis

Answer 9

from front to back through the COM
e.g cartwheel

Question 10

3 descriptors of angular motion

Answer 10

• angular velocity
  -moment of inertia
  -angular momentum

Question 11

angular velocity

Answer 11

is the rate of change in angular displacement or simply the rate of rotation

angular displacement / time taken
measure in radians per second (rad/s)

Question 12

moment of inertia

Answer 12

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

sum of (mass x distribution of there mass from the axis of rotation2)

measured in kgm2

Question 13

mass effect on moment of inertia

Answer 13

the greater the mass of the body the greater the moment of inertia

Hence, sports with high level of twists etc are performed by athletes with low mass as they can rotate easier and stop rotating with ease.

Question 14

distribution of mass from the axis of rotation

Answer 14

the further the mass moves away from the axis of rotation the greater the moment of inertia and resistance to change state of motion

Hence, it is more beneficial to tuck around the axis of rotation as your moment of inertia will be lowered therefore you can rotate more quickly.

Question 15

distribution of mass when running

Answer 15

recovery leg- mass is distributed close to the axis of rotation at the hip therefore moment of inertia is low and the leg moves back down quickly

drive leg- mass distributed further away from the axis of rotation therefore moment of inertia is higher and leg moves slowly

Question 16

moment of inertia’s effect on angular velocity

Answer 16

if moment of inertia is high, resistance to rotation is high therefore angular velocity is low and the rate of the spin is slow

if moment of inertia is low resistance to rotation is low therefore angular velocity is high and spin rate is high

Question 17

angular momentum

Answer 17

the quantity of angular motion possessed on a body

moment of inertia x angular velocity

Question 18

angular analogue of newtons first law

Answer 18

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

Question 19

fluid mechanics

Answer 19

the study of the forces acting on a body travelling through air or water

Question 20

4 factors that affect levels of drag and AR

Answer 20

Velocity - the greater the velocity the greater drag and AR

Frontal CSA - larger the frontal CSA the larger the AR or drag.

Streamlining or shape - more streamlined for aerodynamic the shape of the body in motion the lower the Ar and drag

surface characteristics - the smoother the surface the reduced amount of Ar and drag there is

Question 21

how do skiers minimise AR

Answer 21

smoothness of their lycra
minimise the FCSA by adopting a low couched position
wear tear dropped helmets to create streamlined shape

Question 22

projectile motion

Answer 22

movement of a body through the air following a curved flight path under the force of gravity

Question 23

projectile

Answer 23

a body that is launched into the air losing contact with the ground surface

Question 24

4 factors that affect horizontal distance

Answer 24

speed of release
height of release
angle of release
aerodynamic factors

Question 25

speed of release

Answer 25

links to newtons 2nd law as the greater force applied to the projectile the greater the change in momentum and therefore acceleration in the air

Question 26

angle of release

Answer 26

45 degrees optimal angle

Question 27

height of release

Answer 27

where release is above the landing height the optimal angle is less than 45 degrees e.g shot put and javelin

where release is below landing height the optimal angle is more than 45 degrees e.g bunker shot in golf

Question 28

parabolic flight path

Answer 28

a flight path is symmetrical about its highest point caused by weight being the dominant force

Question 29

non parabolic flight path

Answer 29

a flight path asymmetrical about its highest point as Ar is the dominant force

Question 30

Bernoulli principle

Answer 30

higher the velocity of air flow the lower the surrounding pressure

Question 31

lift force

Answer 31

additional force created by a pressure gradient forming on opposing surfaces of an aerofoil moving through a fluid

Question 32

aerofoil shape impact on lift force

Answer 32

the curved upper surface forces air flow to travel a further distance and therefore move at a higher velocity

flat underneath surface allows air to flow a shorter distance therefore at a lower velocity

velocity increases pressure decreases

Question 33

angle of attack

Answer 33

the most favourable angle of release for a projectile to optimise lift force
discuss is 17 degrees

Question 34

Magnus effect

Answer 34

creation of an additional Magnus force on a spinning projectile which deviates from its flight path

Question 35

Magnus force

Answer 35

a force created from a pressure gradient on opposing surfaces of a spinning body moving through the air

Question 36

hook

Answer 36

a type of sidespin that is used to deviate a projectiles flight path to the left

Question 37

slice

Answer 37

a type of sidespin that is used to deviate a projectiles flight path to the right

Question 38

how Magnus force is created on a topspin shot

Answer 38

• upper surface of the projectile rotating towards the oncoming air flow ( top to bottom) decreasing the velocity of air flow - high pressure zone is created
• lower surface of the projectile rotating the same direction as there air flow increases velocity of air flow therefore a low pressure zone is created

-pressure gradient forming an additional Magnus force being created downwards means the ball ‘dips’ in flight and the flight path shortens