Paper 1 - Biomechanics

Question 1

Define force

Answer 1

A push or a pull that alters, or tends to alter, the state of motion of a body

Something is stationary when the net force is 0 (e.g. gravity one way, your hand the other way OR in space no forces)

Question 2

Define velocity

Answer 2

Velocity - The rate of motion in a particular direction/the rate of change in displacement (speed is the rate of change in distance)

Question 3

Define momentum

Answer 3

Momentum - The quantity of motion possessed by a moving body (momentum increases by speed or weight increasing)

Question 4

Define acceleration

Answer 4

Acceleration - The rate of change of velocity

Question 5

What are newtons 3 laws

Answer 5

1st : Law of inertia
2nd : Law of acceleration
3rd : Law of reaction

Question 6

Newton’s 1st Law of motion (define & examples)

Answer 6

Newton’s 1st Law of Motion - The Law of Inertia
A body continues in a state of rest or in uniform velocity unless acted upon by an external force.
Inertia = laziness in Latin
Everything in the universe is lazy. Force is needed to get it to move, Force is needed to slow it down, stop it, speed it up, or change direction.
E.g. Stationary body will remain at rest until an external force is applied. (Centre pass in netball, ball remains in the player ( C ) hands until a force is applied to pass the ball).
E.g. Moving body will continue to move with constant velocity until made to change its speed and/or direction by an external force. (The ball will travel at constant velocity in the direction thrown until caught by another player).

Question 7

Newton’s 2nd Law of motion (define & examples)

Answer 7

Newton’s 2nd Law of Motion - The Law of Acceleration
When a force acts on an object, the rate of change of momentum experienced by the object is proportional to the size of the force and takes place in the direction in which the force acts.

E.g. The greater the force applied, the greater the acceleration, the greater the momentum, the greater the distance travelled, (Netball shooter close to the ring will only need to impart a small amount of force towards the ring, however further away the shot will need greater force as it needs more momentum to travel to the goal)

Question 8

Newton’s 3rd Law of motion (define & examples)

Answer 8

Newton’s 3rd Law of Motion - The Law of Reaction
For every force that is exerted by one body on another, there is an equal and opposite force exerted by the second body on the first. (For every action there is an equal and opposite reaction).

E.g. For every action there is an equal and opposite reactions (Netball bounce pass, the ball then travels down towards the floor, downward action force of the ground, that is turn exerts an upward force on the ball and the ball bounces up)
(Netball bounce pass, the player exerts an action force of the ball in the downward direction. The ball exerts a reaction force in the upward direction on the player, a slight increase in pressure in the fingers).

Question 9

Define linear Motion

Answer 9

When a body moves in a straight or curved line (curved when a force acts upon it but its velocity is going in one straight direction), with all parts moving in the same direction at the same speed
E.g. tennis ball, satellite in space
Sporting Example : A performer in the skeleton bobsleigh will travel with linear Motion sliding down the straight parts of the track and with linear Motion in a curved line when sliding around the bends.

Angular motion = object has spin therefore is turning

Question 10

What are the different types of force

Answer 10

Action
Reaction
Internal
External
Horizontal/vertical
Net

Question 11

Define action force

Answer 11

Action force = A force exerted by a performer on another body (e.g. the backwards and downwards force entered by the sprinter on the blocks at the start of a race).

Question 12

Define reaction force

Answer 12

Reaction force = An equal and opposite force to the action force exerted by a second body on the first (e.g. the forward and upward reaction force exerted by the blocks on the sprinter at the start of the race)

Question 13

Define internal force

Answer 13

Internal force = Generated by the contraction of skeletal muscle (e.g. 100m contracts the leg muscle to generate the force required to drive away from the block)

Question 14

Define external force

Answer 14

External force = Comes from outside the body and acts upon it. The force of weight, reaction, friction and air resistance

Question 15

Define/explain net force

Answer 15

Net force = Is the sum of all forces accruing on a body (also called resultant force). It is the overall force acting on a body when all individual forces have been considered. (If a net force = 0, there is no change in motion as the forces are balanced). A body will remain at rest or continue to travel with constant velocity.
E.g. rugby scrum (both packs push forwards with equal force, net force = 0)
If a net force is present, there is a change in motion as the forces are unbalanced (a body either accelerates (+ net force), decelerates (- net force), change its direct or change of shape (e.g. + down force)
E.g. if a net force is positive a body will accelerate (when a netball makes a chest pass, the forward force applied is greater than the air resistance so therefore accelerates)
E.g. if a net force is negative a body will decelerate (when a shuttlecock is hit hard it will decelerate rapidly as air resistance acts in the opposite direction of motion)

Question 16

Define horizontal/vertical force

Answer 16

Vertical forces = that push the body up and pull the body down
Horizontal forces = that push a body forwards and pull it backwards

Question 17

5 things a force can do with example

Answer 17

Force can create motion : the football will remain at rest on the penalty spot until a force is applied to make it move
Force can accelerate a body : the greater the force applied on the ball, the greater the acceleration towards the goal
Force can decelerate a body : as the ball moves through the air towards the goal, the force of air resistance will act in the opposite direction and slow it down
Force can change direction of a body : as the goalkeeper dives to save a shot, he will apply a force from his hand to the ball, changing its direction pushing it away from the goal
Force can change the shape of a body : if the goalkeeper fails to make the save, the force of the ball hitting the net will make the net change shape

Question 18

Force calculation

Answer 18

Force calculation : Force (N) = mass (kg) x acceleration (m/s/s)

Question 19

Velocity calculation

Answer 19

Velocity Calculation:
Velocity = displacement / time taken measured in M/s

Question 20

Momentum calculation

Answer 20

Momentum Calculation:
Momentum = mass x velocity measured in kgm/s

Question 21

Acceleration Calculation

Answer 21

Acceleration Calculation:
Acceleration = (final velocity - initial velocity) / time taken measured in M/s/s

Question 22

What are our 2 vertical external forces

Answer 22

Weight (N)
Reaction (N)

Question 23

Explain the external force weight (vertical)

Answer 23

Weight = Weight is the gravitational pull that the earth exerts on a body and is measured in Newtons (N). Weight force is always present and acts downwards from the body’s centre of mass. It’s shown on a diagram as an arrow pointing down from the centre of mass. (Weight = mass x acceleration).

Question 24

Explain the external force reaction (vertical)

Answer 24

Reaction = Reaction is the equal and opposite force exerted by a body in response to the action force placed upon it and its measured in Newtons (N). Newton’s third law of motion says it’s always present when 2 bodies are in contact. This is shown on a diagram by a vertical arrow extending upwards from the point of contact with the surface.

Question 25

What are the horizontal external forces

Answer 25

Friction
Air resistance

Question 26

Explain the external force friction (horizontal)

Answer 26

Friction = Friction is the force that opposes the motion when 2 surfaces are in contact and is measured in Newtons (N). (Eg. A cyclists tyres tend to slip backwards as they rotate, friction opposes this and acts forwards). Friction can be shown on a diagram by a horizontal arrow extending (usually) in the same direction as motion from the point of contact parallel to the sliding surface.

Question 27

4 factors affecting friction

Answer 27

Roughness of the ground surface: By increasing the roughness of the ground surface friction is increased. E.g. Athletes run on rough rubberised track.
Roughness of the contact surface: By increasing the roughness of the contact surface friction is increased. E.g. Sprinters, jumpers and throwers where spikes
Temperature: By increasing the temperature of the ground and contact surface friction is increased. E.g. F1 drivers have a ‘warm-up’ lap on the track
Size of normal reaction: By increasing normal reaction friction is increased. E.g. Shot putters have a high mass (3rd law - greater reaction therefore greater friction in the throwing circle)

Question 28

Horizontal Forces : explain air resistance

Answer 28

Air resistance = Air resistance is a force that opposes the motion of a body travelling through the air and is a form of fluid friction measured in Newtons (N). Air resistance can play a huge role in sport, especially for bodies that travel at high velocities, such as a badminton shuttle. It can be shown on a diagram by a horizontal arrow extending against the direction of motion from the centre of mass.

Question 29

Factors affecting air resistance

Answer 29

Velocity: by increasing velocity air resistance increases; for example, the greater the velocity of a sprint cyclist around the velodrome track, the greater the force of air resistance opposing their motion.
Shape: the more aerodynamic the shape the lower the air resistance. Many sports use a tear-drop or aerofoil shape to minimise air resistance; for example, the shape of a sprint cyclist’s helmet. This is a concept known as streamlining- the creation of smooth air flow around an aerodynamic shape to minimise air resistance.
Frontal cross-sectional area: by decreasing the frontal cross-sectional area air resistance decreases; for example, the low, crouched position of giant slalom skiers in the straights.
Smoothness of surface: by increasing the smoothness of the surface air resistance decreases; for example the smooth Lycra suits of sprinters, cyclists and skiers.

Question 30

Define centre of mass

Answer 30

Centre of Mass = The point at which a body is balanced in all directions. The point from which weight appears to act.

Question 31

Centre of mass : Fosbury Flop Technique

Answer 31

High Jump:
Use a j-curve approach
Plants the outside foot
Drives arm sup lifting the centre of mass
Fully extends the spine to rotate around the bar
Centre of mass passes under the bar

Question 32

Define stability

Answer 32

Stability = The ability of a body to resist motion and remain at rest

Question 33

4 factors affecting stability

Answer 33

Mass of the Body (bigger mass = more stability)

Height of the centre of mass (lower centre of mass = more stability)

Base of support (wider base of support = more stability)

Line of gravity -> centre of mass is over/directly above centre of base/base of support (if centre of mass moves left/right for example there is decreased stability as it isn’t over the base of support)

Question 34

Maximising/minimising stability : sprint start example

Answer 34

Maximise : On your marks
Sprinter preparing in the blocks has maximum stability
The crouched position gives a low centre of mass
The base of support is large, with five points of contact (two feet, two hands, one knee)
The line of gravity falls within the middle of the base of support and sprinters typically have a high mass due to their high proportion of muscle mass
Minimise : Get set
When ‘set’ is called, the sprinter lifts their hips, raising their centre of mass
Lifts one knee reducing the points of contact, and leans forwards shifting the line of gravity to the edge of the base of support
Centre of mass moves forwards to the front of the base of support
This reduces stability ready for movement
When the gun is fired, instability is maximised to aid performance as the centre of mass now falls out of the base of support
Performers own weight supports the movement forward

Question 35

Technology : what is Limb Kinematics

Answer 35

Kinematics is the study of movement in relation to time and space. 3D or optical motion analysis records an athlete performing a sporting action or a patient performing normal bodily movement. This allows joint and limb efficiency to be evaluated with measurements of bone geometry, displacement, velocity and acceleration in multiple planes of movement.

Question 36

Technology : how does limb Kinematics work

Answer 36

Computer software is linked to multiple video or infrared cameras which record, capture and convert the motion shown by the reflective markers placed on the body’s joints and bony landmarks into digital format. The data produced are immediate, objective and highly accurate and can be used by coaches to adjust technique and improve performance (e.g. golf swing or football strike).

Question 37

Technology : what is force plates

Answer 37

Ground reaction forces can be measured in laboratory conditions using force plates. Data from an athlete balancing, running or jumping on a force plate can be used to assess the size and direction of forces acting on the athlete, acceleration rates, work and power output. Most commonly, force plates are used for sports biomechanics assessment, gait analysis (analysis of human motion mainly for running and posture analysis), balance, rehabilitation and physical therapy.

Question 38

Technology : how do force plates work

Answer 38

A force plate is a rectangular metal plate with built in force transducers usually sunk into the ground to become part of the floor. When an object or limb makes contact with the force plate, an electrical output proportional to the force being applied is displayed in graphical format on a computer. The size of the force and time the force is applied can be displayed in three planes of movement. The use of force plates gives immediate, accurate and reliable results that biomechanists can use to analyse performance and health.

Question 39

Technology : what are wind tunnels

Answer 39

F1 teams spend tens of millions getting the aerodynamics of the car right.
McLaren even have their own 145 m long wind tunnel for testing aerodynamic parts and set-ups. Four hundred tons of steel houses a 4 m wide fan that rotates up to 600 rpm. This technology has been used to develop the drag reduction systems (DRS) deployed by trailing cars, reducing the rear flap angle by 4 degrees. This can decrease air resistance (drag) by up to 7 per cent, giving improved chances of overtaking.

Question 40

Technology : how do wind tunnels work

Answer 40

Objects as small as a cycle helmet or as large as an F1 car may be tested for aerodynamic efficiency. The object is placed inside the wind tunnel with instruments to measure the forces produced by the air against its surface. Engineers may also study the flow of air around the object by injecting smoke or dye into the tunnel. The aim of using a wind tunnel is to improve the flow of air around an object, streamlining its path through the oncoming air and potentially increasing lift or decreasing drag.

Question 41

Technology Drawbacks

Answer 41

E.g. Limb Kinematics - Very expensive therefore limited to elite performers. Validity/invalid. Interpretation
E.g. Force Plates - However, they are specialist, expensive and usually housed in laboratory conditions, which can force some performers to adapt the way they run or jump in a real life sporting situation, limiting their potential use. Specific for sports with power so aren’t useful for other sports.
E.g. Wind Tunnels - Needs a lot of space and is expensive which limits this to elite performance. Lab conditions (external factors may affect it).
Overall = Expensive, Reliability, Validity, Subjective, Elitist

Question 42

Strcuture of a lever

Answer 42

Bones act as levers, rigid structures which rotate around a fixed point.
This fixed point is known as the fulcrum and in the human body are the joints.
The muscles that surround a joint create internal forces that move the bones they are attached to.
When a muscle contracts, an effort is created.

Question 43

How a lever works

Answer 43

If this effort is large enough to overcome any load placed upon a lever, such as a weight held in the hand, it will pull on the lever to create movement.
For example, in the upward phase of a bicep curl, the biceps brachii is attached to the radius of the forearm. When the biceps brachii contracts, the muscular force pulls the radius up
towards the shoulder. This is known as flexion of the elbow.

Question 44

First class lever (explain positions and give example)

Answer 44

Fulcrum in middle
E-F-L OR L-F-E

E.g. extension of the neck when preparing to head a football

Diagram on docs

Question 45

Second class lever (explain positions and give example)

Answer 45

Load in middle
E-L-F OR F-L-E
E.g. ball of the foot in the take off phase of a high jump

Diagram on docs

Question 46

Third class lever (explain positions and give example)

Answer 46

Effort in middle
F-E-L OR L-E-F
E.g. flexion of the elbow during a bicep curl

Diagram on docs

Question 47

Define effort arm and load arm

Answer 47

The distance from the fulcrum to the effort is known as the effort arm
The distance from the load to the fulcrum is known as the load arm

Question 48

Define mechanical advantage

Answer 48

Second-class lever systems where the effort arm is greater than the load arm. A large load can be moved with a relatively small effort.

Question 49

Define mechanical disadvantage + the however to this

Answer 49

Third-class lever systems where the load arm is greater than the effort arm. A large effort is required to move a relatively small load.

HOWEVER : Longer levers generate greater forces as the load arm becomes longer and therefore, can give greater acceleration to projectiles (such as a tennis ball or javelin) on release. Therefore, in some sports, such as tennis, taller athletes with longer limbs are at an advantage. This is because it can move the load at high velocity and generate great acceleration over a large range of motion.