Biomechanical movement Flashcards

1
Q

What is Newton’s law of inertia?

A

A force is required to change the state of motion.
The bigger the mass the larger the inertia of the object or body.

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2
Q

What is inertia?

A

Inertia is the resistance an object has to a change in its state of motion.

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3
Q

What is an example of Newton’s first law?

A

In the high jump, the athlete runs horizontally towards the bar and then changes their state of motion at take-off when they travel vertically to try to clear the bar.

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4
Q

What is Newton’s law of acceleration?

A

The magnitude (size) and direction of the force applied to a body determine the magnitude and direction of the acceleration given to a body.
Force = mass x acceleration

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5
Q

What is an example of Newton’s second law?

A

To provide acceleration at the start of a sprint race, an athlete will have to apply a large force internally with their gluteals, quadriceps and gastrocnemius as they drive forward.
A tennis player will impart a large force on the ball, so it accelerates over the net in the direction in which the force is applied.

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6
Q

What is Newton’s law of action and reaction?

A

Every action (force) has an equal and opposite reaction (force).
Action acts on one of the bodies, and the reaction to this action acts on the other body.
Most applications involve Ground Reaction Force.

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7
Q

What is an example of Newton’s third law?

A

At a sprint start, the athlete pushes back on the blocks as hard as possible (action), and the block push forwards on the athlete (reaction) and provides forwards acceleration on the athlete.

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8
Q

What is ground reaction force?

A

The force exerted on the ground by the body in contact with it.
An individual standing still on the ground exerts a contact force (the weight of the individual) and at the same time an equal and opposite ground reaction force is exerted by the ground on the individual.

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9
Q

What is a scalar quantity?

A

When measurements are described in terms of just their size or magnitude, not direction.
Speed, distance, mass and temperature.

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10
Q

What is speed?

A

The rate of change of position.
Speed (m/s) = distance covered (m) / time taken (s)

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11
Q

What is centre of mass?

A

The point of concentration of mass.
For someone standing, it is between the hip region and differs by gender.
Males have more weight concentrated on their shoulders and upper body, so have a slightly higher centre of mass.

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12
Q

What factors affect stability?

A

The height of centre of mass - lowering it increases stability.
Position of line of gravity - should be central over the base of support to increase stability.
Area of the support base - the more contact points, the larger the base and the more stable.
Mass of performer - the greater the mass, the more stability, due to increased inertia.

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13
Q

What are levers?

A

It consists of a fulcrum (pivot), weight to be moved (resistance) and source of energy (effort).
The joints are fulcrums, the effort is provided by muscles, and the resistance is the weight of the body part that is being moved against the force of gravity.

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14
Q

What are first class levers?

A

The fulcrum is located between the effort and the resistance.
In the body, this is the movement of the head and neck during flexion and extension, and the extension of the elbow.

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15
Q

What are second class levers?

A

The resistance lies between the fulcrum and the effort.
The only example in the body is plantarflexion of the ankle.

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16
Q

What are third class levers?

A

The effort lies between the fulcrum and the resistance.
This is found in all other joints of the body.

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17
Q

What is mechanical advantage and disadvantage?

A

This depends on the force arm and the resistance arm.
The force arm is the shortest perpendicular distance between the fulcrum and the application of effort.
The resistance arm is the shortest perpendicular distance between the fulcrum and the resistance.

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18
Q

What is mechanical disadvantage?

A

When the resistance arm is greater than the effort arm.
This means the lever system cannot move as heavy a load but can do it faster.
It also has a larger range of movement.

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19
Q

What is mechanical advantage?

A

When the effort arm is longer than the resistance arm.
The lever system can move a large load over a short distance and requires little force.
It has a small range of movement, and it is difficult to generate speed and distance.

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20
Q

What is the mechanical (dis)advantage of the levers?

A

Second class can generate large forces, but is slow and low RoM.
First and third have large RoM and can move quickly but cannot apply much force to move heavy objects.

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21
Q

What is linear motion?

A

Motion in a straight or curved line, with all body parts moving the same distance at the same speed in the same direction.

22
Q

What is mass?

A

The amount of matter or substance.
Our mass is bone, muscle, fat, tissue, fluid, and is measured in kg.

23
Q

What are examples of scalar quanities?

A

Mass, distance and speed.

24
Q

What are examples of vector quantities?

A

Weight, acceleration, displacement, velocity and momentum.

25
Q

What is weight?

A

The force on a given mass due to gravity.
Mass x gravity = weight (N)
It acts downwards from the centre of mass.

26
Q

What is distance?

A

The length of the path a body follows when moving from one position to another.

27
Q

What is displacement?

A

The length of a straight line joining the start and finish points.
E.g. a 400m racer will have 0 displacement.

28
Q

What is velocity?

A

How fast a body travels in a certain direction.
The rate of change of displacement.
Velocity = displacement / time taken.

29
Q

What are distance-time graphs?

A

Time on x axis, distance y axis.
The line not going up or down shows no distance travelled - stationary.
Constant diagonal direction shows the distance is changing at a constant rate at the same speed.

30
Q

What are distance-time graphs - curves?

A

Gradually steeper curve shows acceleration as more distance being covered in a certain time.
Levelling off curve shows less distance is travelled in a certain amount of time so decelerating.

31
Q

How do you determine the gradient of a graph?

A

Change in the y axis / change in x axis.

32
Q

What are velocity-time graphs?

A

Gradient = change in velocity / time.
If the line goes beneath the x-axis the performer has changed direction.

33
Q

What is acceleration?

A

The rate of change of velocity.
Metres per second squared.
Change in velocity (m/s) / time (s)
Change in velocity (final - intial) / time.

34
Q

What is momentum?

A

The product of mass and velocity of an object.
Momentum (kgm/s) = mass (kg) x velocity (m/s)

35
Q

What is an internal force?

A

It is applied when our skeletal muscles contract.
E.g. force generated as the quadriceps contract concentrically to extend the knee.

36
Q

What is reaction force?

A

Occurs when two bodies are in contact with one another.

37
Q

What is static frictional force?

A

The force exerted on one surface by another when there is no motion between them.
E.g. the friction generated between the surface and someone’s shoe.

38
Q

What is sliding frictional force?

A

When dry friction acts between two surfaces that are moving.
Friction acts in opposition to motion.
Friction resists the sliding motion of two surfaces, and the arrow is drawn in the opposite direction (but same as motion).

39
Q

What is friction affected by?

A

The surface characteristics of the contact bodies. Spikes on shoes increase friction and maximise acceleration.
The temperature of the surfaces, increasing temp reduces friction.
The larger the mass of the objects the greater the friction.

40
Q

What is air resistance?

A

It opposes the motion of a body travelling through the air. Depends on:
The faster the velocity, the greater the air resistance.
The larger the cross-sectional area, the greater the air resistance.
The smoother/ more streamlined the less resistance.

41
Q

What are examples of reducing air resistance?

A

Cyclists crouch low over their handlebars, not upright, to reduce cross-sectional area.
Many swimmers shave off body hair to create a smooth surface.

42
Q

How are weight and reaction forces shown on a free body diagram?

A

Weight force is drawn down from the centre of mass.
Reaction force starts where two bodies are in contact with one another.
It is drawn in an upward direction.

43
Q

How are friction and air resistance forces shown on a free body diagram?

A

Friction starts where the two bodies are in contact and is opposite to the direction of any potential slipping. Same direction as motion.
Air resistance is drawn from the centre of mass, opposing the direction of motion.
The longer the length of the arrow, the larger the magnitude or size.

44
Q

What is net force - balanced?

A

The resultant force acting on a body when all the forces have been considered.
When standing, weight force and reaction force are equal in size but opposite in direction, so there is zero net force.

45
Q

What is net force - unbalanced?

A

When jumping, the performer accelerates upwards as the reaction force is bigger than weight force.
If friction arrow is longer than the air resistance arrow, the body accelerates.

46
Q

What is impulse?

A

The time it takes a force to be applied to an object or body.
Impulse (Ns) = force x time.

47
Q

What is impulse and momentum?

A

Increase in impulse results in an increase in the rate of change of momentum.
Momentum = mass - acceleration.

48
Q

What is an example of using impulse to increase momentum?

A

Increase the amount of muscular force applied.
e.g. large force generated when jumping for a rebound in basketball.
Increase the amount of time the force is applied. e.g. 3-4 turns in hammer throw not just 1.

49
Q

What is an example of using impulse to decrease momentum?

A

Increase the time forces act upon them.
Indoor athletics, the athlete pushes their feet hard into the ground to increase the contact time of the foot with the ground so they decelerate quickly.

50
Q

What are force-time graphs?

A

Small negative impulse, large positive impulse (positive net impulse), shows the sprinter is accelerating.
Equal postive and negative impulse shows sprinter at constant velocity.
Large negative, small positive impulse (negative net impulse) shows the sprinter is decelerating.