Biomechanics Flashcards
What is projectile motion?
Anything launched into the air (only influenced gravity and air resistance) becomes a projectile motion.
Projectiles have both a vertical and horizontal component.
What is biomechanics?
Biomechanics is the study of living things from a mechanical perspective and is essentially the physics behind human movement.
What is the vertical component?
How high and how long it’s in the air for.
What is the horizontal component?
How far it goes.
Vertical component is influenced by….
gravity and force of projection
Horizontal component is influenced by
Air resistance
Factors affecting flight path of a projectile are…
Angle of projection/release
Speed of projection/release
Height of projection/release
Angle of projection is..?
The angle at which an object is released into the air.
The angle of projection can be…
Horizontal
Vertical
Oblique/parabolic
How is the height of released calculate?
By subtracting the height of the projectile is released from the height at which it stops/needs.
Height of projectile - height of landing = relative projection height
What is the optimum angle of projection when the height of release is 0 degrees?
45 degrees
What is the speed of release influenced by?
It is influenced by the vertical component which determines the height reached and the flight time of an object and the horizontal component/force, which determines the horizontal distance covered by the object.
What is the optimum angle of projection when when the height of release is < 0 degrees?
More than 45 degrees
What is the optimum angle of projection when the height of release is >0 degrees?
Less than 45 degrees
What is laminar?
When objects move through air or water slowly, they do not disturb the flow a great deal and the air or water will flow in a smooth, parallel manner around the object = laminar flow.
What is turbulent flow?
When objects move through air or water rapidly they disturb the flow to the point that layers next to the surface of the object get mixed together.
What is buoyancy?
The upwards force acting on a body within water.
What does the buoyant force equal?
Buoyant force= weight of the fluid displaced by an object
The greater the density a fluid has…. (in relation to buoyancy)
…the more buoyant objects will be when placed in this medium.
What happens when buoyancy force and weight are equal?
The object will float.
What happens when the weight of an object is greater than the buoyancy force?
The object will sink.
What is drag force?
When an object moves through a fluid or when a fluid flows around a stationary object.
What is drag force known as in air?
Air resistance
What is drag force known as in water?
Hydrodynamic resistance.
What is bernoulli’s principle?
It explains how as the velocity of fluid increases the pressure decreases. This causes an area of turbulence behind the object where pressure is less than in front of the object.
Forces will always….
…act from the area high pressure, to an area of low pressure.
What does streamlining do?
It decreases turbulence created at the back of an object and thus also reduces drag.
Drag is affected by what factors?
The shape of an object and how streamlined it is
The density of the fluid (air or water)
The velocity of the object as it moves through the fluid
The cross-sectional area of the object in the direction of motion
What is lift force?
Is a force acting on an object in a fluid in a direction perpendicular to the flow of a fluid.
What is lift force affected by?
The velocity of the fluid
The density of the fluid
The size, shape and position of the object
Foil shape
Angle of the object relative to the direction of flow
The Magnus effect
Uneven surface coatings
What is a foil shape?
A foil has a curved and a flat surface which causes fluid to flow faster over the curved surface than the flat one which leads to pressure differences.
Lift force is generated from the….
…area of high pressure to the area of low pressure.
What is the angle of attack?
The angle between the long axis of the object and the direction of air/water flow.
To create a lift force what type of angle of attack is required?
A positive angle.
Lift can be created by…..
…spin (topspin, backspin and sidespin) and the deviation towards the direction of the spin.
What is the Magnus force?
The lift force generated by a spinning ball.
Air will travel across a smooth surface…
…quicker than over a rougher surface.
Turbulent air from the rougher surface is at…
…lower pressure than that flowing over the smooth surface which is at higher pressure.
What is the Magnus effect?
The deviation in the direction of a spinning object towards the direction of the spin.
Chapter
6
What is inertia?
Inertia is the tendency of an object to resist change in it’s state of motion.
The greater the inertia….
…the harder it is to move or change the state of motion of an object.
Inertia is directly proportional to….
…the mass of the object.
The more mass…
…the greater the force needed to change it’s state of motion.
What is mass?
Mass is the amount of matter an object is made up of.
What is weight?
Weight is the force exerted on an object by gravity and is directly proportional to its mass.
How do you calculate the weight of an object?
Weight = mass x acceleration caused by gravity (9.8 m/s^2)
= measured in Newtons
What is Newton’s First Law of Motion?
A body will remain at rest or in a state of constant motion unless acted upon by an external force (inertia).
What is Newton’s Second Law of Motion?
A force applied to an object will produce a change in motion (acceleration) in the direction of the applied force that is directly proportional to the size of an object.
What do forces produce?
Forces can produce movement or change the motion of an object.
How do you work out force?
Force = mass x acceleration F = m x a F(N) m(kg) a(m/s^2)
What is Newton’s Third Law of Motion?
For every action there is an equal and opposite reaction.
What is friction?
Friction is one of many forces that can be applied to objects (including gravity, weight, air and water resistance).
Friction happens when…
…two objects come into contact with each other and it opposes motion of the object(s).
What is momentum?
Momentum is how much motion an object has.
How do you work out momentum?
Momentum = mass x velocity
How much momentum does an object that isn’t moving have? And why?
- Because it has no velocity.
If two objects have the same mass but different velocities, which one has the greater momentum?
The one moving quickest has the greater momentum.
If two objects have the same velocity but different masses, which one has the greater momentum?
The one with the greater mass also has the greater momentum.
What is the conservation of momentum?
Total momentum before a collision equals the total momentum after the collision.
What is the First Law of Angular Motion?
The angular momentum of a body remains constant unless acted upon by an external torque.
What is the Second Law of Angular Motion?
A torque applied to an object will produce a change in angular motion in the direction of the applied torque that is directly proportional size of the torque and inversely proportional to the moment of inertia of the object.
What is the Third Law of Angular Motion?
For every torque there is an equal and opposite torque.
What is the moment of inertia?
The moment of inertia is the resistance of an object to changes in its angular motion = mass x radius^2.
How do you work out angular momentum?
Angular momentum = the moment of inertia x angular velocity
An object whose mass is closer to the axis of rotation is easier to rotate than one whose mass is further away.
D DJ
What is angular momentum?
Is the quantity of angular motion of an object.
How is angular momentum conserved?
It is conserved when a body is in flight and there is an inverse relationship between angular velocity and moment of inertia.
What is the summation of momentum?
The sequential and coordinated movement of each body segment to produce maximum velocity.
When is maximum velocity created?
When momentum is generated in a sequential or summed manner from larger body parts close to the centre of gravity to those further away.
What is impulse?
The product of a force and the time period over which it is applied, which is equal to the change in momentum of an object.
To change the momentum of an object the amount of time a force is applied to it needs to change.
D did
How do you work out impulse?
Impulse = force x time
Impulse can be applied to….
…increase or decrease the velocity of an object.
What is linear motion?
The movement of a body along a straight or curved path where all body parts move in the same direction at the same speed.
What is angular motion?
Involves rather rotation around a central axis or fixed point.
What is a torque?
The tendency of an object to rotate.
What is a projectile?
An airborne body that is only affected by the forces of gravity and air resistance.
