1.3 Flashcards
define angular distance
angle through which a body has rotated in moving from first position to the second
define angular displacement
shortest change in angular position/smallest angle through which a body can rotate to reach the second position from the first
value for angular distance when gymnast does double somersault
720*
value for angular displacement when gymnast does double somersault
0*
define centre of mass (2)
position in body which it is balanced in all directions; point at which the mass of a body is said to be concentrated/said to act
describe how performer applies eccentric force to ball (2)
is an off centre force; force applied outside the centre of mass of the ball
effect of an eccentric force on a ball (2)
create spin/angular motion/rotation; causes swerve/lift/deviation in flight
define the analogue of newtons first law of motion
a body will rotate with constant angular momentum unless acted upon by an external angular force
how a figure skater controls angular velocity while performing multiple spin about longitudinal axis (7)
AM=AV x MI; AM generated at start when off centre force applied to skater by the ice; start low AV; during arms/legs brought in to reduce MI; increases AV; at end arms/legs out to increase MI; reduce AV to prevent over rotation
define linear motion
movement in a straight line
explain how linear motion is created
direct force / force applied through centre of mass
velocity equation
velocity = distance / time
acceleration equation
acceleration = change in velocity / time
explain the concept of conservation of angular momentum using the angular analogue of newtons first law of motion (7)
a body will continue to rotate with constant AM; unless acted upon by eccentric force; AM = MI x AV; once in flight any change in MI will cause a change in AV to conserve AM; eg if diver tucks MI reduced so AV increases (means AM conserved during flight); performer can manipulate body shape to change MI and AV as AM remains constant
define angular motion (2)
movement of a body (in a circular path) about an axis of rotation; rotation of a body around an axis
explain how angular motion is generated to produce a somersault (2)
force applied outside CoM/axis of rotation; eccentric force
describe linear motion
movement of a body in a straight line and all parts move the same distance, in the same direction, in the same time
describe angular motion
movement of a body in a circular path about an axis of rotation
identify vertical forces acting on gymnast in a handstand and explain their relationship during the handstand (3)
weight and reaction force; W = R; forces are equal in size and opposite in direction/net force = 0/ forces are balanced
define angular velocity (2)
rate of change in angular displacement; speed of rotation
units of angular velocity
radians per second
why a gymnast in a bridge is more stable than a handstand (5)
more points of contact with the floor; larger base of support; lower centre of mass; line of gravity at centre of/falls further within the base of support; line of gravity easier to keep in centre of base of support
describe angular motion (2)
movement around an axis; generated by an eccentric force
example of angular motion
gymnast swings on or around the bar
use newtons laws of motion to explain how a sprinter can maximise performance during a sprint start (3)
1 - sprinter will remain stationary unless an unbalanced force acts on him; 2 - greater net/resultant/forward force on the sprinter the greater the sprinters acceleration; 3- sprinter applies force back and down into floor so ground applies equal up and forward force on sprinter
describe what is meant by inertia of a moving object (6)
inertia is resistance of a body to change its state of motion; depends on mass (bigger mass greater inertia); resistance to accelerate; resistance to decelerate/stop; resistance to change direction; larger inertia, greater force required to change its state of motion
define moment of inertia (2)
resistance of a body to start or stop rotating; resistance of body to change its state of angular motion
explain factors that affect MI of rotating object (5)
depends on mass of an object; greater mass = greater MI; depends on distribution of mass from axis of rotation; further away from axis = greater MI; greater MI = greater force required to increase or decrease rate of spin/rotation
explain why a runner has a flexed knee during the recovery phase of stride action (4)
flexed knee means mass of leg is closer to axis of rotation/mass distribution decreases; so MI lower; less force required to move leg through recovery stage; recovery can be quicker/increase stride rate
describe the term friction (3)
friction occurs when two surfaces slide over one another; friction acts in opposite direction to motion; friction acts parallel to the two surfaces in contact
describe how different factors can change amount of friction generated, eg for each (4)
rough surface means more F eg boots, tyres/smooth surface means less F eg skis; greater downforce means more F eg spoilers on F1 cars; greater (normal) reaction force means more F eg games player pressing into ground to change direction; hotter means more F eg tyres, roads, ski slopes
explain how performers maximise stability, eg for each (4)
lower CoM eg ski jumper bend knees on landing; increase size of base of support/more points of contact eg rugby widen stance in contact situation/gymnastics bridge; increase body mass eg NFL put weight on so harder to knock over; make line of gravity central to base of support EG?; make line of gravity closer to resistance force/point of contact eg rugby player lean forward into tackles
describe why a performer might want to minimise stability using egs (6)
reduce movement time eg set position in sprint start in 100m; increase speed eg lean forward when running to make line of gravity outside base of support; change direction quickly eg when swerving in rugby; rotate from take off eg leaning forward to jump with spin in somersault; decrease stability of ball in flight by using no spin eg penalty apply force through CoM; increase stretch eg defending in netball line of gravity outside base of support
define the term friction
The resistance to motion of two moving
objects or surfaces that touch
how rugby player can increase stability (5)
CoM over base of support; lower CoM by bending knees; increase area of base by widening stance; line of gravity in centre of base of support; line of gravity in centre of base of support forwards/player leans forwards
explain how perfomer can move theri CoM outside the body effectively
fosbury flop; in flight jumper arches their back; CoM will follow pre determined flight path; CoM may pass under bar while jumper clears bar; can clear greater heights with same effort
explain how a performer can increase friction to optimise performance using egs (5)
increase roughness contact eg sprinter wears spikes to increase F which helps them run faster; increase roughness ground eg tarmacadam track in athletics; increase normal reaction force eg shot putter high mass to increase normal reaction and F to prevent over rotation; increase downforce eg spoiler on F1 cars increase F to increase speed; increase *C eg F1 warm up lap
apply newtons laws of motion to explain how a basketballer would jump to block a shot (4)
1 - to leave ground player must exert greater force into ground than their weight/reaction force >weight; 2 - accelerate upwards; greater forces, greater acceleration/higher jump; 3 - player pushes down onto ground and ground applies equal and opposite force upwards onto player
describe factors affecting friction during performance (4)
rough/smoothness of footwear; rough/smoothness of surface/ground; size of downforce/normal reaction force; temperature of surface
explain why some performers would want to maximise friction using egs (4)
to accelerate eg sprinter wears spikes to aid grip; to slow down/stop eg skier turns skiis sideways to slow; to change direction eg footballer studs to enable to turn quickly; to impact spin on an object eg slice in shot in table tennis
explain the factors that affect stability (6)
more stable if CoM lower; more stable with larger area of base of support; increase number points of contact can increase area of base; more stable if greater mass; more stable if line of gravity/CoM nearer the centre of the base of support; distribution of body parts can affect CoM which can affect stability (raise arms raises CoM which reduces stability)
which of newtons laws is most applicable to a speed skater achieves constant velocity as they travel round the track
first
define momentum
the quantity of motion (possessed by a moving object) or the impetus gained by a moving object
equation for momentum
mass x velocity
explain what is meant by net force (3)
sum of all forces acting on a body; 0 is forces are balanced; positive/negative if unbalanced
compare what is meant by ‘balanced forces’ and ‘unbalanced forces’ (3)
B v U; two or more opposing forces are equal in size v not equal; no change in motion v change in motion; constant velocity/rest v acceleration/deceleration occurs
describe how a performer can increase their acceleration use egs (5)
increase speed/force eg sprinter apply greater force to blocks/track; increase friction eg long jumper wear spikes to increase F with ground; reduce mass eg high jumper lose weight prior to competition; improve technique eg runner adjust body position so more force generated in a forward direction; reduce AR eg sprint cyclist adopts streamline shape to minimise AR
apply netwons second law to show how a hockey player may maximise the balls acceleration (7)
acceleration is proportional to size of force applied; hockey player applies larger force to increase A; size of force dependent on velocity of stick as it hits ball; player attempt to max velocity of stick on hit; size of force dependent on mass of stick; may use heavier stick to increase force; heavier stick will maximise acceleration as long as velocity of stick is not lost (can swing heavy stick as fast as light one)
describe the changes in the position of the CoM at take off and during flight that maximise performance in the fosbury slop technique (7)
take off: CoM raised by lifting arms/knee; CoM stays inside body; flight: high jumper rotates about CoM; CoM moved outside body by arching back; CoM passes under bar; while high jumper passes over bar; enabling greater height to be achieved
explain the term balanced force, using eg (3)
two or more forces acting are equal in size and opposite in direction or net force = 0 or no change in motion/constant velocity/stationary; eg rugby scrum
explain the term unbalanced force, using eg (3)
two or more forces are not equal in size or net force is present or change in motion/deceleration/acceleration; eg tennis serve
moment of force equation
force x distance from fulcrum
advantage of 3rd class lever (2)
move load through large range of movement; speed of load faster than speed of effort; generate faster speeds/acceleration
units for MI
kgm2
describe how the force of weight acts on a sporting body (3)
downward force; acts from CoM; due to gravity
explain factors that can affect AR, use egs (5)
decrease front cross sectional area decrease AR eg sprint cyclist tuck head and lift knees; smooth air flow around shape decrease AR eg shape of discus; smooth surface decrease AR eg shave legs, lycra clothes; increase speed increase AR eg high speed of sprinter; air density decrease AR decrease eg javelin travels further at altitude
eg of second class lever (2)
press up where fulcrum is toes/feet; standing on tip toes to defend a shot in netball
why second class lever mechanical advantage (5)
effort arm longer than load arm; can move large load with relatively small effort/large loads more efficiently; closer the load is to fulcrum the greater the advantage; greater distance between load and effort, greater advantage; mechanical advantage = effort arm / load arm
how elbow can act as fulcrum for two different lever systems (4)
1st: eg tricep extensions, tennis serve, throwing, fulcrum in middle, EFL; 3rd: bicep curls, effort in middle, FEL
how force plates enhance performance (7)
analyse posture; analyse gait/running/walking; improve balance; rehabilitation; measure force/power; prevent injury on landing; prostheses design
eg of 2nd class lever (2)
calf raise; take off phase of high jump at ankle
eg of 3rd class lever (2)
bicep curl; knee extension when kicking ball
explain relationship between size of vertical forces and their impact on size of resulting vertical jump for a basketballer (4)
reaction force > weight means theres an unbalanced force on player; means there is a net upwards force; so upwards acceleration; bigger reaction force, greater net upward force/upwards acceleration/height achieves
factors that affect horizontal distance travelled by a projectile (4)
height of release; speed of release; angles of release; air resistance/shape/spin of object
explain shape of flight path of a shot (3)
parabolic; weight is dominant force; AR low as speed is low
