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AS PE > 3.1 Biomechanical principles: Newton's Laws of motion, force and the use of technology > Flashcards

3.1 Biomechanical principles: Newton's Laws of motion, force and the use of technology Flashcards

1
Q

What is the definition of force

A

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

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2
Q

What is Newton’s first law?

A

A body continues in a state of rest or uniform velocity unless acted upon by an external or unbalanced force.

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3
Q

What is Newton’s first law also known as?

A

the law of inertia

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4
Q

What is a practical example of Newton’s first law?

A

The 100m sprinter will remain at rest in the blocks until an external force large enough to overcome their inertia creates motion. Equally, when the sprinter reaches a constant velocity, they should continue at that constant velocity until an external or unbalanced force acts upon them to change.

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5
Q

What is the definition of inertia?

A

The resistance of a body to change its state of motion, whether at rest or while moving.

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6
Q

What is the definition of velocity?

A

The rate of change in displacement.

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7
Q

What is Newton’s second law?

A

A body’s rate of change in momentum is proportional to the size of the force applied and acts in the same direction as the force applied.

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8
Q

What is a practical example of Newton’s second law?

A

The greater the force applied to the sprinter, the greater the rate of change in momentum and therefore acceleration away from the blocks. The force is applied in a forward direction and so the sprinter drives towards the line.

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9
Q

What is the definition of momentum?

A

the quantity of motion possessed by a moving body

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10
Q

What is the equation for momentum?

A

p = mv

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11
Q

What is the definition of acceleration?

A

the rate of change in velocity

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12
Q

What is the equation for acceleration?

A

a = v-u/t

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13
Q

What is Newton’s third law?

A

For every action force applied to a body, there is an equal and opposite reaction force.

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14
Q

What is a practical example of Newton’s third law?

A

When the 100m sprinter applied a down and backward action force into the blocks, the blocks provide an equal and opposite up and forward reaction force to the sprinter to drive them out of the block.

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15
Q

How would you apply all three of Newton’s Laws of motion to a rugby conversion kick?

A

1 - The rugby ball will remain at rest on the conversion tee until an external force is applied by the rugby player’s foot to the ball.
2 - The greater the size of the force applied by the rugby player to the ball, the greater the rate of change in momentum and acceleration towards the post. The rugby ball will accelerate in the same direction as the force applied towards the post.
3 - A forward and upward action force is applied to the rugby ball from the rugby player’s foot. The rugby ball will apply an equal and opposite down and backward reaction force to the player’s foot.

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16
Q

What are the two types of force?

A

Internal force
external force

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17
Q

What is internal force?

A

Internal force is generated by the contraction of skeletal muscle.

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18
Q

What is a practical example of an internal force?

A

A 100m sprinter must contract the rectus femoris to extend the knee and gastrocnemius to plantar flex the ankle to generate the force required to drive away from the blocks.

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19
Q

What is external force?

A

External force comes from outside the body and acts upon it.

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20
Q

What are some examples of external forces?

A

weight
reaction
friction
air resistance

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21
Q

Using a football penalty, what are the 5 effects that force can have?

A

1 Force can create motion - the football will remain at rest on the penalty spot until a force is applied to make it move.
2 Force can accelerate a body - the greater the force applied by the footballer’s foot to the ball, the greater the rate of acceleration towards the goal.
3 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.
4 Force can change the direction of a body - as the goalkeeper dives to save a high corner shot, he will apply a force from his hands to the ball, changing its direction pushing it away from the goal.
5 Force can change the shape of a body - if the goalkeeper fails to make the save, the force of the ball coming into contact with the net will make the net change shape.

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22
Q

What are the 5 effects that force can have?

A

1 create motion
2 accelerate a body
3 decelerate a body
4 change the direction of a body
5 change the shape of a body

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23
Q

What is the definition of net force?

A

The sum of all forces acting on a body, also termed as resultant force. It is the overall force acting on a body when all individual forces have been considered.

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24
Q

What is the definition of balanced forces?

A

These occur when two or more force acting on a body are equal in size and opposite in direction. The body will remain at rest or in motion with a constant velocity.

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25
Q

When the forces are balanced, what does this mean for the net force?

A

net force = 0

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26
Q

What is the definition of unbalanced forces?

A

These occur when two forces are unequal in size and opposite in direction. A net force will be present and the body will change its state of motion , either accelerating or decelerating.

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27
Q

What is weight?

A

the gravitational pull that the Earth exerts on a body

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28
Q

What is the reaction force?

A

the equal and opposite force exerted by a body in response to the action force placed upon it

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29
Q

What is friction?

A

the force that opposes the motion of two surfaces in contact

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30
Q

What are the 4 factors that friction is affected by?

A

1 roughness of the ground surface
2 roughness of the contact surface
3 temperature
4 size of normal reaction

31
Q

How does the roughness of the ground surface affect friction?

A

By increasing the roughness of the ground surface, friction is increased

32
Q

What is an example of athletes maximising friction through the roughness of the ground?

A

athletes run on rough, rubberised tracks

33
Q

How does the roughness of the contact surface affect friction?

A

By increasing the roughness of the contact surface, friction is increased?

34
Q

What is an example of athletes maximising friction through the roughness of the contact surface?

A

sprinters, jumpers and throwers all wear spikes shoes

35
Q

How does temperature affect friction?

A

By increasing the temperature of the ground and contact surface, friction is increased.

36
Q

What is an example of athletes maximising friction through temperature?

A

F1 drivers have a warm-up lap on the track

37
Q

How does the size of the normal reaction affect friction?

A

By increasing normal reaction, friction is increased.

38
Q

What is an example of athletes maximising friction through the size of the normal reaction?

A

Shot-putters have a high mass and due to Newton’s third law of motion this creates equal and opposite high reaction force. This allows greater friction in the throwing circle, helping to prevent over-rotation.

39
Q

What is air resistance?

A

the force that opposes the motion through the air

40
Q

What is streamlining?

A

the creation of smooth air flow around an aerodynamic shape to minimise air resistance

41
Q

What are the 4 factors that air resistance is affected by?

A

1 velocity
2 shape
3 frontal cross-sectional area
4 smoothness of surface

42
Q

How does velocity affect air resistance?

A

By increasing velocity, air resistance increase.

43
Q

What is an example of velocity increasing air resistance?

A

The greater the velocity of a sprint cyclist around the velodrome track, the greater the force of air resistance opposing their motion

44
Q

How does shape affect air resistance?

A

The more aerodynamic the shape, the lower the air resistance.

45
Q

What shapes are often used in sports to minimise air resistance?

A

tear-drop or aerofoil shape

46
Q

What is an example of an athlete using shape to affect their air resistance?

A

The shape of a sprint cyclist’s helmet minimises their air resistance. This concept is known as streamlining - the creation of smooth air flow around an aerodynamic shape to minimise air resistance.

47
Q

How does frontal cross-sectional area affect air resistance?

A

By decreasing the frontal cross-sectional area, air resistance decreases.

48
Q

What is an example of frontal cross-sectional area affecting air resistance?

A

The low, crouched position of giant slalom skiers in the straights.

49
Q

How does the smoothness of the surface affect air resistance?

A

By increasing the smoothness of the surface air, air resistance decreases.

50
Q

What is an example of how smoothness of surfaces affect air resistance?

A

the smooth Lycra suits of sprinters, cyclists and skiers.

51
Q

What is the definition of a free body diagram?

A

a clearly labelled sketch showing all of the forces acting on a body at a particular instant in time.

52
Q

Where should weight be drawn from on a free body diagram?

A

from the centre of mass extending vertically downwards

53
Q

Where should reaction be drawn from on a free body diagram?

A

from the point of contact extending vertically upwards

54
Q

Where should friction be drawn from on a free body diagram?

A

From the point of contact and usually extending horizontally in the same direction as motion (parallel to the surfaces)

55
Q

Where should air resistance be drawn from on a free body diagram?

A

from the centre of mass and extending horizontally against the direction of motion

56
Q

In which sports is weight minimised and why?

A

Weight is a force minimised by certain athletes, such as ballet dancers. This low weight means they have a low inertia and can therefore create motion with little force, ensuring fast changes of direction and great vertical acceleration in leaps.

56
Q

In which sports is weight limited and recorded and why?

A

Boxers and jockeys endure strict weight limits for performance. Most athletes want to maximise their percentage of muscle mass to generate as high a force on contraction as possible.

57
Q

In which sports is reaction force maximised and why?

A

Reaction force is often maximised by athletes who vertically accelerate, such as high jumper. High jumpers lean back as they drive their weight down into the ground and rock from their heel to toes to extend the time the action force is applied to the track. due to Newton’s third law of motion, the greater the action force the greater the reaction force. When couples in the internal force of muscular contraction, as the arms swing and leg extends, a greater height is achieved.

57
Q

In which sports is the reaction force maximised and why?

A

The effect is maximised in events such as gymnastic vaulting where the reaction force is amplified due to the recoil of the spring board, increasing vertical acceleration. Vertical ground reaction forces are also minimised by using sprung floors, which absorb some of the landing forces, helping to prevent overuse, repetitive strain and impact injuries of dancers, gymnasts and basketball players.

58
Q

What is kinematics?

A

the study of movement in relation to time and space

59
Q

What does limb kinematics allow you to see?

A

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.

60
Q

What are the advantages of limb kinematics?

A

The data produced are immediate, objective and highly accurate and can be used by coaches to adjust technique and improve performance.
The motion can focus on a specific limb or piece of equipment and analyse technique in preparation, execution and recovery phases of motion.

61
Q

What are the disadvantages of limb kinematics?

A

The accuracy and repeatability of results depends on the correct placement of the bodily markers and the mathematical principles the results are based upon do not cater for individual differences.
This technique is highly specialised, expensive and largely limited to laboratory conditions, making some sporting actions difficult.

62
Q

How are force plates used to analyse movement?

A

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.

63
Q

What are force plates used for?

A

Sports biomechanics assessments, gait analysis (analysis of human motion mainly for running and posture analysis), balance, rehabilitation and physical therapy

64
Q

How do force plates work?

A

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 form on a computer. The size of the force and time the force is applied can be displayed in three planes of motion.

65
Q

What are the advantages of force plates?

A

The use of force plates gives immediate, accurate and reliable results that bio mechanists can use to analyse performance and health.

66
Q

What are the disadvantages of force plates?

A

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.

67
Q

What is the definition of reliability?

A

The extent to which a experiment, test or measuring procedure gives the same results after repeated trials.

68
Q

What is the definition of validity?

A

How well a test measures what it claims to measure. It is important for a test to be valid in order for the results to be accurately applied and interpreted.

69
Q

How do wind tunnels work?

A

The object (such as a cycle helmet) 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.

70
Q

Why are wind tunnels used?

A

The aim of using wind tunnels is to improve the flow of air around an object, streamlining its path through the oncoming air and potentially increasing lift or decreasing drag.

71
Q

What are the advantages of wind tunnels?

A

They allow engineers to have tight control on environmental variables such as wind speed or wind direction, and gives them the ability to control cross winds and measure air resistance and flow with precision accuracy in a very time-efficient manner.

72
Q

What are the disadvantages of wind tunnels?

A

There are very specialised facilities mainly housed in engineering bases.
They are very expensive and require complex analysis of the results by research professionals.

AS PE (16 decks)

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