biomechanics Flashcards
what does biomechanics mean ?
Biomechanics is the study of how the body moves, how it applies forces to itself and other objects that it comes in contact with.
what is force
This is where an object at rest can be changed by the pushing or pulling of an object.
for example a body in motion can be slowed, speeded or have it’s direction altered by a force exerted upon it.
How to calculate speed ?
distance/time
How to calculate velocity ?
displacement/time
What is acceleration ?
This represents the rate of change in velocity (vector quantity)
How to calculate acceleration ?
change in velocity (V(end)-U(start) divided by time taken to complete change (t)
measured in m/s squared
What is newtons first law
everybody at rest or moving with constant velocity in a straight line will continue in that state unless compelled to change by an external force exerted upon it.
this is known as the law of inertia
e.g. the ball at rest or moving at constant velocity will continue moving in a straight line unless compelled to change by an external force.
What is newtons 2nd law
the acceleration of a body is proportional to the force causing it and the acceleration takes place in the direction the force acts.
this is known as the law of acceleration
e.g. if they kick the ball with greater force it will accelerate further
what is newtons 3rd law ?
when an object exerts a force upon another object there is a force equal in magnitude but opposite in direction exerted by the second object on the first.
this is known as the law of action and reaction.
e.g. when she kicks the ball it will be equal in magnitude but opposite in direction
what is weight ?
this is the force due to gravity
mass x gravity= 9.8g often rounded up to 10.
what is a net force
this is a force in one direction that can cancel ou4t a completely equal force in the opposite direction
what is friction
friction is a force which acts on the interface of surfaces which are in contact and acts in the opposite direction to the direction in motion.
the size of the frictional force determines the ease or difficulty of movement of the objects in contact.
how is the force of friction increased/decreased
- by increasing surface areas in contact with one another e.g. slides at swimming pools
- by increasing the force that presses the surface areas together e.g. mountain bikers sit over the steering wheel to gain a better grip.
- by increasing the amount of molecular interaction between 2 surfaces e.g. floors are swept to remove perspiration enabling a firmer grip
factors that effect the force of friction ?
1.Roughness of the surface
2.Greater the downforce
3.Warmth of surface
4. Air resistance
on a velocity/time graph what is a dist
the area under the line
what is fluid resistance
air resistance is a form of friction, the friction of air molecules against the surface of an object.
it opposes motion
what factors affect the degree of resistance
- the velocity of the moving object (faster the object the higher the resistance)
2.the frontal cross sectional area - the shape and surface characteristics of the moving body
what is a projectile
a projectile is said to have both vertical and horizontal velocity both are independent of one another. E.g ball. The movement is the parabola
what is a vector diagram
it illustrates the direction and magnitude of the motion.
the arrow indicates it’s direction
the size of the arrow indicates it’s magnitude
What factors act on a object that is airborne (projectile)
Air resistance and gravity so only vertical motion can be affected by gravity as it’s always constant and acts vertically downwards . horizontal won’t though and any changes to it will be due to air resistance
What factors can affect or maximise the horizontal displacement a projectile can travel
ANGLE OF RELEASE
if release height and landing height is equal e.g.long jump
then the optimum angle of release is 45 degrees
VELOCITY OF RELEASE
an increase in the velocity of a projectile will increase its horizontal displacement when compared to an object of lesser velocity
HEIGHT OF RELEASE
an increase in the release height will increase the horizontal displacement of the projectile.
What is the moment of inertia
This is the objects reluctance to spin
Inertia- mass of body x distance from axis of rotation squared
How to workout angular momentum
Angular velocity x moment of inertia
What is and how to work out momentum
It is the amount of motion a body possesses, Mass x velocity
What is the Bernoulli effect
-It involves the idea of airflow and pressures, for example if there is a high airflow there will be low pressure and vice versa for example the spoiler on a formula 1 car
- when the air flow changes so does the pressure if there’s a low flow——)high pressure if there’s a high flow—)low pressure
Stages of the Bernoulli principle
-The air flow above the foil has to travel a further distance therefore its speed must increase so the pressure lowers.
- the airflow below the foil has to travel a shorter distance therefore it’s speed can decrease and the pressure increases
- a pressure gradient is created due to 2 contrasting pressure concentrations being close to one another so as this exists air moves from high to low
What is the magnus effect
- this is where for example there is a ball which spins and it causes the airflow on one side to move fast meaning a fast flow —) low pressures and air is pulled over
- there is a gradient which moves in a high to low
- on the other side it resists air which the flow is slow but the pressure is high
Stages of the magnus effect
-If the ball is spinning backwards it affects the air flow lines.
- the air flow lines above the ball are moving with the direction of the spin therefore causing the air speed to increase
- the air line below the ball opposing the direction of the spin causes the air speed to decrease
- the backspin causes high pressure beneath the ball which creates a lift
- the top spin creates a low pressure on top of the ball creating a downward force
What is drag
Drag and air resistance is the same thing it is the friction of air molecules acting on a object
What is laminar flow
-This is the flowing in layers
-the smooth flow of air past a object seen as minimal drag and turbulent flow is seen as high drag
How would you attempt to reduce fluid friction when cycling
- firstly get behind someone so they can absorb the air molecules
- surface characteristics
- reduce the direct contact with airflow seen as drafting
- removing resistance from the surface such as Lycra and shave
- reduce your forward cross sectional area
Technology-
1. Handle bar design and width
2. Clothing
3.riding posture
4. Hand position on bars
5. Wheel design
Explain the relationship between moment of inertia and angular velocity
-The moment of inertia is the objects reluctance to spin
- the moment of inertia is influenced by mass and its distribution
- angular momentum= MOI X AV
- when a object is rotating momentum is conserved
- therefore if the moment of inertia is altered the velocity will be affected
For example if a spinning ice skater brings there arms inwards the angular velocity increases but if they bring there arms outwards it decreases
Describe the factors which determine the amount of fluid friction acting on a swimmer
- Speed of the swimmer
- Forward cross section (size of the person)
- Surface characteristics
- Surface area in contact with water
- Avoidance of water surface effects
Explain the term turbulent flow and how the bobsleigh is used to minimize this factor
Turbulent flow is high drag which is the friction of air molecules on an object.
- at low speeds air flow past a object is laminar meaning air flows in layers
- when this flow is interrupted by going to fast or by a prostrusion which is the upsetting of streamlined shapes the air is thrown out into vortices and the layers mix up and there is turbulent flow (the resistance is greater)
When does linear motion occur
This is where a body moves in a straight or curved line with all the parts of the body moving the same distance in the same direction at the same speed
Quantities of this is
1. Vector/scalar quantity vector has magnitude and direction but scalar just has magnitude
2. Inertia
3. Acceleration
4. Mass
5. Speed
6. Displacement
7. Momentum
8. Weight
9. Velocity
10. Distance
What is the difference between distance and displacement
The quantity of distance refers to the amount of ground an object covers during its motion but displacement considers how far the position of the object has changed as a result of the motion.
Difference between speed and velocity
Speed is the rate of change of distance of a bodies movement per unit of time and has no consideration for direction e.g. speed= distance/time
Velocity is the rate of change of displacement and is a vector quantity and is direction aware e.g. velocity= displacement/time
What is impulse
It is another way on thinking about force and it is concerned with the length of time a force is applied to a object or body and relates to a change in momentum
Force x time
Impulse is used to add speed to a body or object or slow down moving bodies
What is the difference between balanced and unbalanced force
Balanced force occurs where there are 2+ forces in operation equal of size but opposite in direction, all the forces cancel each other out so that 0 is the net force so a object will either remain stationary or if moving it will continue to move at constant velocity.
Unbalanced forces occur where a force is acting in one direction is larger than that acting in the opposite direction so the object or body will start to move or accelera/decelerate in the direction of the bigger force
What are the 2 types of forces
Vertical forces
1. Weight
2. Normal reaction
Horizontal forces
1. Friction
2. Air resistance
What is angular motion
This occurs whenever a force acts outside the center of mass of a body or object this is called an eccentric force.
E.g. in gymnastics when doing a back flip they lean backwards just before take off so the internal force generated by her leg muscles passes outside the center of mass and initiates rotation
Quantities of this is angular…
1. Distance
2. Displacement
3. Speed
4. Velocity
5. Acceleration
