Topic 4.3: Biomechanics Flashcards
1
Q
Scalars and Vectors
A
- Scalar quantity has only magnitude (size)
- Vector quantity has both magnitude and direction
2
Q
Distance
A
- Distance (d) – How far an object travels
- Does NOT depend on direction
3
Q
Displacement (s)
A
- The difference between an object’s final position and starting position
- DOES depend on direction
4
Q
Speed
A
- A scalar quantity that measures how fast an object is moving
- “The rate at which an object covers distance.”
- An object with no movement at all has a zero speed.
5
Q
Velocity
A
A vector quantity that measures both the speed and direction of an object’s motion.
6
Q
Speed vs Velocity
A
- Speed = how fast you are travelling
- Velocity = speed in a given direction
7
Q
Equation for Velocity
A
speed (velocity) = distance travelled/time taken
8
Q
The Formula Triangle
A
- distance = velocity x time
- velocity (speed) = distance / time
- time = distance / velocity
9
Q
Acceleration (a) m/s²
A
- Rate at which an object changes its velocity
- change in velocity, direction or both = acceleration
It’s calculated using the equation:
- acceleration = change in velocity / change in time
- change in velocity = final velocity - initial velocity
- change in time = finish time - start time
10
Q
What is a force?
A
A push or pull upon an object resulting from the object’s interaction with another object
11
Q
4.3.7 Define Newton’s three laws of motion.
A
Law 1: The Law of Inertia
Law 2: The Law of Acceleration
Law 3: The Law of Action/Reaction
12
Q
Newton’s First Law
A
- Inertia is the natural tendency of an object to resist changes in motion
- If an object is motionless, it will want to remain motionless, if an object is moving, it will want to continue moving at same speed, same direction, unless acted upon by an unbalanced force
- The more mass….the more inertia
13
Q
Newton’s Second Law
A
- When forces are unbalanced in a particular direction, there is a NET FORCE
- forces are balanced (no net force) = travels at constant velocity
- Acceleration is proportional to net force
- Mass is inversely proportional to net force
- net force = mass x acceleration
- F = ma
14
Q
Newton’s Third Law
A
- Every action has an EQUAL and OPPOSITE reaction
- When two objects interact, there is a force on each object
- magnitude of force on first object = magnitude of force on second object
- direction of force on the first object is opposite the direction of force on the second object
15
Q
Momentum
A
The quantity of motion of a moving body, measured as a product of its mass and velocity
- Momentum (kg.m/s) = Mass (kg) x Velocity (m/s)
- p = mv
16
Q
The relationship between
mass and velocity for momentum
A
- 2x mass = 2x momentum
- 4x velocity = 4x momentum
- Linear relationship
17
Q
4.3.3 Define the term centre of mass.
A
- Point at which the mass and weight of an object are balanced in all directions
- The lower the centre of mass the more stable the object
- Can be outside the body aswell
18
Q
Base of Support
A
- The location on a body or object where most of the weight/mass is supported.
- The larger the area the base covers, the more stable the object will be.
19
Q
Line of Gravity
A
- An imaginary vertical line through the centre of mass/gravity straight down to the earth
- If the line of gravity falls within the object’s base of support the, the object is relatively stable
- If the line of gravity falls outside of the base of support, the object is relatively unstable
20
Q
Stability
A
Stability is dependant on the COM being directly above the BOS
21
Q
Factors Affecting Stability
A
- Position of the Centre of Mass
- Position of the Line of Gravity
- Mass of the Athlete
- Size of the Base of Support
22
Q
Torque
A
A force that rotates a body about an axis
23
Q
Angular (Rotational) Momentum
A
- Amount of angular (rotational) movement
- The ice skater will continue to spin until another torque acts to change that state.
24
Q
Conservation of angular momentum
A
- The angular momentum of a system remains constant unless acted on by an external torque
- To slow down (rotation), increase moment of inertia (for example opening arms in the skater example)
- To increase speed (rotation), decrease moment of inertia (for example bringing arms close to the body)
25
Angular Momentum Formula
Angular Velocity x Moment of Inertia
26
Angular velocity
the rate of change of angular position of a rotating body
27
4.3.11. Explain the factors that affect projectile motion at take-off or release.
Angle of Release
Speed of Release
Height of Release
28
Optimal Release Angle
Depends on release height and landing height
RH > LH = < 45˚
RH = LH = 45˚
RH < LH = > 45˚
29
Speed of release
* The magnitude of the projectile’s velocity vector at the instant of release
* When projectile angle and height are held constant, speed of release will determine range
30
Height of release
If speed of release = angle of release for two shot-put athletes, the taller athlete has an advantage;
31
Bernoulli’s Principle
* Velocity and pressure have an inverse relationship
* Fluid velocity **increases**, pressure **decreases**
* Fluid velocity **decreases**, pressure **increase**
32
Magnus Effect on Top Spin
**Top of ball:**
Surface of ball is travelling opposite to air flow → air slow down → high pressure
**Bottom of ball:**
Surface of ball is travelling the same direction of air flow → air speeds up → low pressure
**Consequences:**
Pressure difference cause ball to deviate toward area with lower pressure → dips to the ground
33
Magnus Effect on Back Spin
**Top of ball:**
* High velocity flow → low pressure
**Bottom of ball:**
* Low velocity flow → high pressure
**Consequences:**
* Ball deviate towards area with lower pressure → stays up longer
34
Principles of Levers
Levers are…
* Simple machines that help us apply force.
* Rigid structures, hinged at some part with forces applied at two other points.
35
All levers have three parts...
* **Fulcrum (Axis)** - The pivot point
* **Load (resistance)** - The weight that needs to be moved
* **Effort** - The force that is applied to move the resistance (or load)
36
Functions of a Lever
increase the load (or force)
increase the velocity
37
4.3.5. Distinguish between first, second and third class levers.
* If F is in the middle: 1st class
* If R is in the middle: 2nd Class
* If E is in the middle: 3rd Class
38
First Class Levers
39
Second Class Lever
40
Third Class Lever
41
Impulse
* To change momentum we need to apply an impulse
* j = force x time
* Impulse = the change in momentum
* Impulse is the area under the force-time graph
