Biomechanics Flashcards
1
Q
What is the definition of Mass?
A
Mass is the quality of matter the body possesses
2
Q
Acceleration is…
A
the rate of change of velocity
3
Q
How would you calculate acceleration?
A
Change in velocity (ms-1)
———————————– = Acceleration (m/s2)
Time (seconds)
4
Q
Displacement (m)
———————— =
Time Taken (s)
A
Velocity (metres/second)
5
Q
This is the gravitational force exerted on an object and the unit is Newtons (N)
A
Weight
6
Q
EQUATION: How is speed measured?
A
Distance covered (m)
------------------------------ = Speed (m/s)
Time taken (s)
7
Q
The path a body takes as it moves from the starting to the finishing point
A
Distance
8
Q
The product of the mass and velocity of an object. Measured in kgm/s
A
Momentum
9
Q
What is displacement?
A
The shortest route in a straight line between starting and finishing point (A to B quickest)
10
Q
EQUATION: Weight (kg) =
A
Mass (kg) x gravitational field strength (N/kg)
11
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
12
Q
What is Newton’s First Law of Motion also known as?
A
The law of inertia
13
Q
What does Newtons First Law of Motion state?
A
A force is required to change the state of a motion
14
Q
The law of acceleration is also called…
A
Newtons Second Law of Motion
15
Q
What is Newtons Second Law of Motion?
A
The magnitude (size) and direction of the force determines the magnitude and direction of the acceleration.
AKA. Force = mass x acceleration (F=ma)
16
Q
This law describes what happens when two bodies (or objects) exert forces on one another - equal and opposite reaction (e.g. a goalkeeper)
A
Newtons Third Law of Motion - the law of action/reaction
17
Q
The point of balance of a body…
A
the centre of mass
18
Q
Why does the centre of mass always change?
A
As the body is constantly movinh
19
Q
Who’s centre of mass is slightly higher in the body? Males or females?
A
Males as more weight is concentrated in their shoulders and upper body whereas females have more body weight at their hips
20
Q
Give FOUR factors affecting stability?
A
- The HEIGHT of the centre of mass - lower increases stability
- Position of the line of gravity should be central over the base support to increase stability
- Area of the support base - more contact points increases stability
- MASS of performer - greater mass increases stability due to increased inertia
21
Q
What are the two measurements used in linear motion?
A
- Scalar quantity
2. Vector quantity
22
Q
Scalar quantity is…
A
Only described in terms of size or magnitude
E.g. mass, distance and speed
23
Q
Vector quantity is…
A
Described in terms of magnitude (size) and direction
E.g. weight, acceleration, displacement, velocity and momentum
24
Q
What does a force do?
A
Change a body’s state of motion
25
Give an example of two types of forces
Internal force - skeletal muscles contract
| External force - outside the body
26
Give an example of a specific External force
Air resistance, friction, weight and gravity
27
Using a high jumper, explain why a large internal force from the leg muscles is needed?
To create a big action force in order to achieve as much vertical displacement (height) as possible
28
When drawing forces using vectors, how is the magnitude/size of the force reflected?
Through the length of the arrow drawn
29
EQUATION: Impulse =
force x time
30
What will an increase impulse result in?
An increase in the rate of change of momentum which causes a large change in velocity
31
How can using impulse to increase momentum be achieved?
Through increasing the amount of muscular force that is applied and through increasing the amount of time in which a force is applied
Impulse = force x time
32
Give an example of how a gymnast can use impulse to decrease momentum
When landing the gymnast flexes her hip, knee and ankle which extends the time of force on the ground (how long the feet are in contact with the mat) and this allows the gymnast to control the landing
33
Using a 100m sprinter in a race, how does impulse effect the race?
1. START OF THE RACE = the net impulse is positive which shows the sprinter is accelerating.
2. MIDDLE OF THE RACE = both positive and negative impulses are equal (net impulse is zero) which means the sprinter is running at a constant velocity
3. END OF THE RACE = the net impulse is negative which shows the sprinter decelerating
34
Static and Sliding are two types of what?
Friction
35
When does Static friction occur?
Before an object starts to slide
36
What friction is occurring between two surfaces that are moving relative to one another?
Sliding friction
37
State three factors that affect friction?
1. The surface characteristics of the two bodies/objects in contact
2. The temperature of the two surfaces in contact
3. The mass of the objects that are sliding
38
How does a 100m sprinter wearing running spikes increase friction?
As the spikes make contact with the track and therefore maximise acceleration
39
Raising the temperature causes a increase or reduction in friction?
Reduction
E.g. sweeping action ion the ice so a curling stone can travel further
40
A larger mass results in...
greater friction
41
What does air resistance and drag depend upon in order to take effect?
1. The velocity of the moving body - faster means more resistance
2. The cross-sectional area of the moving body - larger area means greater resistance
3. The shape and surface of characteristics of a moving body - streamlined shape results in less resistance
42
Give an example of how a cyclist will try reduce air resistance against them?
They reduce their cross-sectional area when on the bike by crouching low over the handlebars, rather than sit upright
43
Give a sporting example of how an athlete would reduce air resistance/drag by altering their shape and surface characteristics
A swimmers will shave off body hair before a race to create a smooth surface. They would also wear a swimming cap and tight racing suits to reduce drag.
44
How is the gradient of a graph determined?
Changes in the y axis
------------------------------
Changes in the x axis
45
In velocity time graphs, what does it mean if the curve goes below the x axis?
There has been a change in direction
46
What is meant by horizontal displacement?
The shortest distance from the starting point to the finishing point in a line parallel to the ground
47
Give three factors that determine the horizontal displacement of a projectile
1. Angle of release - when both release height and landing height are equal, then the optimum angle of release is 45 degrees
2. Speed of release - the greater release velocity of the projectile, the greater the horizontal displacement travelled
3. Height of release - a greater height release increases the horizontal displacement
48
What two factors affect if a flight path is a true parabola or a distorted parabola?
Weight and Air Resistance
49
What is a parabola?
A uniform curve that is symmetrical at its highest point (ie matching left and right side)
50
Give a sporting example of a parabola flight path
A shot put - a large mass so there is a longer weight around than air resistance during the flight path. The longer the flight path, the longer air resistance can have a greater influence
51
How does a shuttlecock flight path reflect a distorted parabola flight path?
It has a lighter mass and an unusual shape that increase Air Resistance. As the shuttlecock continues its flight path, the effect of air resistance reduces
52
What is the horizontal component
The horizontal motion of an object and it remains constant during flight
53
What is the vertical component?
The upward motion of an object and it decreases during flight
54
This is the rate of change of angular velocity over time measured in rads/s2
Angular acceleration
55
This is the rotational speed of an object and the axis about which the object is rotating
Angular velocity
56
This is the smallest change in angle between the starting and finishing point
Angular displacement
57
What is Angular Motion?
The movement around a fixed point or axis such as a somersault
58
When does Angular Motion occur?
Occurs when a force is applied outside the centre of mass
59
Angular momentum (L) =
Moment of Inertia (I) x Angular Velocity
60
Moment of inertia is...
the resistance of a body to angular motion (rotation)
61
What does moment of inertia depend upon?
The mass of the body and the distribution of mass around the axis.
The greater the mass, the greater the resistance to change and therefore the greater moment of inertia
62
What is Angular momentum?
Conserved quantity - it stays constant unless an external torque acts upon it (newtons first law)
63
Explain how a figure skater can manipulate their moment of inertia to change speed of their spin?
- Legs and arms stretched out at the start of the spin, which increases the distance from the axis of rotation, resulting in a a large moment of inertia and a large angular momentum in order to start the spin = decrease in speed/angular velocity
- Arms and legs brought in with line of body means the distance of these body parts to the axis of rotation decreases reducing the moment of inertia, meaning that angular momentum has to increase also = increase in speed/angular velocity
64
What is Newton's First Law in relation to Angular Motion?
A rotating body will continue in its state of angular motion unless an external force is exerted upon it
65
What is newton's Second Law in relation to Angular Motion?
The rate of change of angular momentum of a body is proportional to the force causing it and the change in direction in which the force acts
66
Give an example of Newton's Second Law- Angular Motion
Leaning forward from a diving board will create more angular momentum than standing straight
67
Give an example Newtons Third law of Angular Motion
A goalkeeper during a jump to stop the ball- arms up, lower part of his legs will go back (in opposite direction)
68
What is another word for a force?
Torque = a rotational force
69
What is drag?
A resistance force caused by the motion of a body travelling through a fluid ( air or water)
70
What does a drag force do?
Slow something down
71
This is the friction between the surface of an object and the fluid environment
Surface drag = 'skin drag' (surface of body)
72
This is the impact of the fluid environment on an object
Form drag = 'shape drag' (shape of body)
73
Name three factors that reduce and increase drag
1. Velocity - greater velocity, greater the drag force
2. Cross-sectional area - larger = greater drag force
3. The shape and surface characteristics - streamlined?
74
What are we referring to when we mention the Bernoulli Principle
Upward and downward lift force on objects
75
What is the angle of attack?
The tilt of a projectile relative to the airflow. Changes the flow of air around an object so the air travels over the top of the object
76
Explain how a high angle of attack will affect the distance travelled by a discus?
1. The discus will not travel as far
2. A high angle of attack will mean the discus produces less lift/more drag
3. As a result, air begins to flow less smoothly over the top of the discus
4. Meaning the air flow over the top of the discus becomes more and more separated
77
Describe how a lift force can be generated by a discus in flight
1. Air molecules under the surface of the discus are accelerating
2. this causes a pressure difference between the upper and lower surfaces of the discus
3. creating a pressure gradient
4. creating an upward lift force/Bernoulli effect
78
How does a downward lift force occur?
There is higher pressure and a slower velocity of molecules above the surface than below the surface
79
What effect does a downward lift force have on a Formula 1 car?
Greater frictional force so the tyres maintain a firm grip on the track as it travels at high speed and around corners
80
What components does a lever consist of?
Fulcrum (a pivot), Weight (resistance) and Effort (source of energy)
81
What are the two main functions of a lever?
1. To increase the SPEED at which the body can move
| 2. To increase the amount of resistance that can be overcome
82
What is a First Order Lever?
The Fulcrum is between the Effort and Resistance
______________________________________
Effort ^ Fulcrum Resistance
83
What is a Second Order Lever?
The Resistance is between the Fulcrum and Effort
____________________________________
^Fulcrum Resistance Effort
(e.g. plantarflexion at the ankle)
84
Give an example of a Second Order Lever?
Plantarflexion at the ankle
85
What is a Third Order Lever?
Responsible for majority of movements in the body (apart from extension at elbow = 3rd and Plantarflexion = 2nd)
The Effort is between the Fulcrum and Resistance
_____________________________________
^Fulcrum Effort Resistance
86
Give an example of a First Order Lever?
Extension at the elbow
87
What is a mechanical advantage in terms of levers?
When the force arm is longer than the resistance arm = more force and power
88
What is a mechanical disadvantage in terms of levers?
When the resistance arm is greater than the force arm = can't lift as heavy load but is quicker and a larger range of movement
