Mechanics Of Movement

Question 1

Newtons First Law

Answer 1

• a body will continue in its state of rest or motion in a straight line unless compelled chambers that state by external forces exerted upon it
• a penalty- the ball will remain on the spot unless the player kicks it

Question 2

Newtons Second Law

Answer 2

• the rate of change of momentum of a body is proportional to the force causing it and the change that takes place in the direction in which the force acts
• when a player kicks the ball the acceleration will depend on the size of the force- Hardee’s it kicked the further it goes

Question 3

Newtons Third Law

Answer 3

• to every action there is an equal and opposite reaction
• football header
• when the footballer jumps a force is exerted on the ground in order to gain height- at the same the ground exerts an upward force upon the footballer

Question 4

What is a Linear Motion?

Answer 4

• a motion in a straight or curved line with all body parts moving the same distance at the same speed and in the same direction

Question 5

Measurements of linear motion are:

Answer 5

MASS- a physical quantity expressing the amount of matter in our body

WEIGHT- the force on a given mass due to gravity

INERTIA- the resistance of an object has to a change in its state of motion

DISTANCE- the length of the path a body follows when moving from one position to another

DISPLACEMENT- the length of a straight line joining the start and finish points

SPEED- the rate of change of position

VELOCITY- rate of change of displacement

MOMENTUM- the product of the mass and velocity of an object

Question 6

Scaler Quantities

Answer 6

• describe size or magnitude- mass, inertia, distance and speed

Question 7

Vector Quantities

Answer 7

• describe size and direction- weight, acceleration, deceleration , displacement, velocity and momentum

Question 8

Forces and Vectors

Answer 8

• force is a vector quantity- has size, direction as well as point and line of application

Vector Forces
- Weight- gravitational force pulling down

• Reaction- occurs whenever two bodies are in contact

Horizontal Forces
- Friction- occurs when two bodies are in contact with each other have a tendency to slip

• Air Resistance- dependant on the velocity, cross section shape and surface characteristics

Question 9

What is impulse?

Answer 9

• the time it takes a force to be applied to an object or a body and is often related to change in momentum

Question 10

Projectile Motion

Answer 10

• an object in motion is dependant on:

1) angle of release
2) Height
3) Velocity

Question 11

Factors affecting projectiles

Answer 11

1) weight and air resistance effect it
2) projectiles with a large weight have a small air resistance and follow parabolic flight path
3) air resistance has a greater effect on projectiles with a lighter mass causing them to deviate from a parabolic pathway

Question 12

Axes of rotation

Answer 12

1) Transverse- side to side
2) Frontal- front to back
3) Longitudinal- top to bottom

Question 13

Angular Momentum

Answer 13

• it is rotation
• it involves an object in motion around an axis
• depends on the moment of inertia and angular velocity

Question 14

Using ‘Newton’s First’ and ‘Second Laws of Motion’, explain how the swimmer dives off
the starting blocks. (4 marks)

Answer 14

A. Force is applied by the muscles

Newton’s First Law of Motion/Law of inertia
B. Performer will remain on the blocks unless a force is applied
C. Performer continues to move forwards with constant velocity until another force is applied
D. Water slows the swimmer

Newton’s Second Law of Motion/Law of Acceleration

E. Mass of swimmer is constant
F. Greater the force exerted on the blocks, the greater the
acceleration/momentum
G. Force governs direction

Question 15

Heptathletes are required to complete the 200metre sprint.
A 200metre runner must exert a large force in a short period of time to generate an impulse. Sketch and label a graph to show the impulse generated during the acceleration phase of a 200metre race. (3 marks)

Answer 15

A. X Axis – (time)/milliseconds/seconds
B. Y Axis – (force)/Newton’s
C. Shape of graph – negative and positive components of force shown
with negative first
D. Positive impulse clearly larger than negative impulse
E. Positive and negative (force) labelled

Question 16

Using Newton’s Second Law of Motion, explain how an athlete is able to accelerate towards the finish line. (3 marks)

Answer 16

A. Mass of runner is constant
B. Force = Mass x Acceleration
C. Greater the force exerted on the floor, the greater the acceleration/ momentum/proportional
D. Force governs direction
E. Force provided by muscular contraction
F. Ground reaction force

Question 17

Elite golfers use their clubs to overcome the forces acting on the golf ball so that it travels long distances.
(a) Describe how the impact of the golf club, gravity and air resistance affect the velocity and acceleration of a golf ball. (4 marks)

Answer 17

Golf club
1. Applies force
2. Gives acceleration/changes momentum/velocity
Gravity
3. Only affects vertical component of flight
4. Reduces/negative effect on velocity/decelerates
Air resistance
5. Negligible
6. Affects horizontal components
7. Reduces/negative effect on velocity/decelerates

Question 18

(b) The flight of a golf ball is said to be parabolic. Explain the term parabolic and the main factors that limit the distance that a golf ball will travel in flight. (4 marks)

Answer 18

1. Left and right sides match/mirror each other/inverted U shape/symmetrical (if
   accompanied by diagram)
2. Height of release – higher height above landing more distance
3. Angle of release – closer to 45° the better/affects height and distance
4. Speed of release – more force/speed gives more distance
5. Design of golf ball/dimples

Question 19

What forces act on a player when they are running during a game? (3 marks)

Answer 19

1. Gravity;
2. Friction/Air resistance;
3. Action force/muscular forces/reaction forces/ground reaction force/GRF.

Question 20

During the game, a performer kicks a ball. Describe the effects of forces on the flight of the ball. (4 marks)

Answer 20

1. Muscular forces cause change in motion;
2. Gravity limits height of flight/pulls it back down;
3. (Gravity) reduces vertical component;
4. Air resistance/friction affects distance of flight;
5. (Air resistance) reduces horizontal component;
6. Can be negligible – short duration/short passing;
7. Can be large – long flight/passing. 4 marks

Question 21

Explain, using the idea of vectors, how these same muscle groups can produce both maximal horizontal motion and maximal vertical motion. (5 marks)

Answer 21

(a) 1. Vectors have magnitude/size;
2. Vectors have direction;
3. Point of application;
4. Line of application; sub max 3
5. Force applied to ground by muscles contracting
6. Equal and opposite reaction force moves performer/GRF producing the movement;
7. Vertical and horizontal components to vectors;
8. Sprinter requires large horizontal component/high jumper requires large vertical component;

Question 22

The acceleration that a performer achieves when sprinting or high jumping is related to impulse. What do you understand by the term impulse, and how does the athlete use impulse during their sprint or take-off? (3 marks)

Answer 22

(b) 1. Force x time/Ft;
2. Equates to change in momentum/mv-mu; sub max 2
3. Constant mass;
4. Impulse has direction;
5. Single footfall;
6. Positive impulse for acceleration at take off;
7. Negative impulse when foot lands/breaking action;
8. Net impulse positive equals acceleration;
9. Graph annotated

Question 23

Use Newton’s Three Laws of Motion to explain how a tennis player moves towards the ball in preparation to play a stroke. (5 marks)

Answer 23

A. First Law – reluctance to change state of motion/constant motion/ uniform
motion/velocity;
B. Force required to change state of motion/overcome inertia of player;
C. Muscle contractions; (Sub max 2 marks)
D. Second Law – magnitude/size of force governs change in momentum;
E. Mass remains constant;
F. Force governs magnitude of acceleration given to player;
G. And direction; (Sub max 2 marks)
H. Third Law – equal and opposite reaction force;
I. Force applied to ground/ moves performer;
J. Ground Reaction Force. (Sub max 2 marks)
Max of 5 marks
Do not credit Force = Mass x Acceleration
Only credit responses that relate to the player not the ball.

Question 24

Explain, in terms of the player moving towards the ball, the difference between velocity and acceleration. (3 marks)

Answer 24

A. Velocity = rate of change of displacement/displacement ÷ time;
(Not speed, not distance)
B. How fast/quickly player moves towards ball;
C. Acceleration (not speed) = rate of change of velocity/change in velocity ÷ time (taken to change)/[Vf - Vi] ÷ time/a = !v ÷ t;
D. Push off ground to accelerate (not speed)/change velocity;
E. (Both) have direction/are vectors.

Question 25

Name the forces acting on the ball while it is in the air and explain how these forces affect the ball’s flight path. (4 marks)

Answer 25

(a) A. Gravity and friction/air resistance; B. Ball’s motion has vertical and horizontal components; C. Gravity decreases vertical component/acts downwards/affects height; D. From positive to negative; E. Friction/air resistance affects horizontal component/distance/speed/slows; F. Negligible/doesn’t change/stays the same

Question 26

Use Newton’s three laws of motion to explain how a performer can move towards the ball in one of these games. (4 marks)

Answer 26

1. (First Law) force required to change state of motion (of performance); 2. (Second Law) size of force governs change of momentum; (do not credit F=MA) 3. Mass remains constant; 4. Force governs the magnitude of the acceleration given to the ball; 5. And direction; 6. (Third Law) equal and opposite (ground) reaction force; 7. Performer applies force to ball through muscle contractions.

Question 27

In hockey, golf and rugby, the performer may hit or kick the ball into the air, where it becomes a projectile. Explain how the various forces involved act to affect a projectile during its flight. (3 marks)

Answer 27

c) 1. Parabolic flightpath/trajectory/parabola; 2. Gravity reduces height achieved/brings projectile back to earth; 3. Acts on the vertical component; 4. Air resistance has no negligible effects; 5. Horizontal components of most sports projectiles; 6. Some projectiles affected by air resistance/shape – golf ball dimples

Question 28

Using Figure 2, explain the mechanical principles that allow spinning ice-skaters to adjust their rate of spin. (6 marks)

Answer 28

b) 1. Ice may be regarded as a friction free surface/friction is negligible; 2. During spins angular momentum remains constant; 3. Angular momentum is the quantity of rotation; 4. Angular momentum = angular velocity x moment of inertia; 5. Angular velocity = rate of spin/how fast skater spins; 6. Moment of inertia = distribution/spread of mass around axis; 7. Changing/reducing moment of inertia affects/increases angular velocity; 8. Skater brings arms into body allowing rate of spin to increase. (Accept annotated diagrams/graphs)

Question 29

Explain how a gymnast can alter the speed of rotation during flight and outline how plyometrics can assist in their preparation to achieve maximum lift at take-off. (14 marks)

Answer 29

Altering speed of rotation A.Changingtheshapeofthebodycausesachangein speed B. Changeinmomentofinertialeadstoachangeof angular velocity/speed/spin of rotation/ angular moment; C. Angularmomentumremainsconstant(during rotation) D.AngularMomentum=moment of inertia angular velocity E. Angularmomentum-quantityofrotation/motion F. Angular velocity - speed of rotation G. Moment of inertia - spread/distribution of mass around axis/reluctance of the body to move To slowdown(rotation)gymnast increases moment of inertia I. Achieved by extending body/opening out/or equivalent J. To increase speed (of rotation) gymnast decreases moment of inertia K. Achieved by tucking body/bringing arms towards rotational axis Plyometrics L. Description of activity – hopping/bounding/ depth jumping/medicine ball work M. Aim – develop power/speed/explosive strength N. InvolvesFastTwitchFibres/Type2 O. Eccentric muscle contraction happens first P. followedbyconcentriccontraction Q. Stretch Reflex activated R. Detectedbythemusclespindles S. Sendsnerveimpulsetospinalcord/central nervous system/CNS/afferent impulses T. Elastic energy stored U. Protectsoverstretchingofmuscles/avoid injury V. Threephases–stretchshorteningcycle

Question 30

Using Newton’s Laws of Motion, explain how a player moves towards a ball during a rally and outline how the force of muscle contraction can be varied to ensure that skills are executed correctly. [14 marks]

Answer 30

Newton’s Laws of Motion A. Forceisappliedbythemuscles/muscularcontraction B. (Newton’sFirstLawofMotion)-Lawofinertia C. Performerwillremainstationaryunlessaforceisapplied/force applied to overcome state of inertia D. Performercontinuestomovetowardstheballwithconstant velocity until another force is applied E. Musclesactingasbrakeslowstheperformer F. (Newton’s Second Law of Motion) - Law of Acceleration G. Force = Mass x Acceleration / F = MA H. Massofperformerisconstant I. Greater the force exerted on the ground, the greater the acceleration/momentum towards the ball J. Ground reaction force K. Forcegovernsdirection L. (Newton’s Third Law) Law of action and reaction/action reaction M. equal and opposite reaction force; N. Forceappliedtogroundmovesperformer Muscle contraction O. Size of motor units recruited/larger for greater contraction/smaller for less powerful P. Multipleunitsummation Q. Number of units recruited/more or less R. Typeofmusclefibresizedeterminesforceofcontraction/fast twitch fibres rather than slow twitch fibres for more powerful contractions S. Allornonelaw/Allornothinglaw/orexplanation/actionpotential or threshold is reached / contraction occurs in all of the fibres in the motor unit T. Wave summation U. frequencyofimpulse/innervations V. Motorunit(muscle)unabletorelax/increasetheforce W. Tetanus/tetanic for powerful contraction X. Musclespindlesdetectchangesinmusclelength/speedof contraction Y. Sendinformationtobrain/CNS Z. Compares information to long term memory to ensure correct force applied/past experiences AA.Spatial summation BB.rotating the frequency of the impulse to motor units to delay fatigue/some work while others rest or equiv.

Question 31

The major leg muscles used in the drive phase of sprinting are the gastrocnemius, quadriceps, gluteals and hamstrings. Exactly the same muscle groups are also used in high jumping. a) Explain, using the idea of vectors, how these same muscle groups can produce both maximal horizontal motion and maximal vertical motion. (5 marks)

Answer 31

1) Vectors have magnitude/size; 2. Vectors have direction; 3. Point of application; 4. Line of application; 5. Force applied to ground by muscles contracting 6. Equal and opposite reaction force moves performer/GRF producing the movement; 7. Vertical and horizontal components to vectors; 8. Sprinter requires large horizontal component/high jumper requires large vertical component

Question 32

The acceleration that a performer achieves when sprinting or high jumping is related to impulse. What do you understand by the term impulse, and how does the athlete use impulse during their sprint or take-off? (3 marks)

Answer 32

1. Force x time/Ft; 2. Equates to change in momentum/mv-mu; 3. Constant mass; 4. Impulse has direction; 5. Single footfall; 6. Positive impulse for acceleration at take off 7. Negative impulse when foot lands/breaking action; 8. Net impulse positive equals acceleration; 9. Graph annotated;