Chapter 5 PowerPoint Flashcards
What is kinematics?
The study or description of the spatial (3D world) and Temporal (time) characteristics of motion without regard for causative forces.
Kinematics can be said to be: Form or technique used to describe ____ with respect to ____?
Form or technique used to describe movement with respect to time
What two general aspects of observation does kinematics involve?
Qualitative: Visual Observation
Quantitative: Measuring, Biomechanist’s researching factors limiting performance
What are five visually observable aspects of technique or form?
Patterns
Sequencing
Shapes
Angles
Lines
What is motion?
Motion – Change in position with respect to a reference point
What is distance?
Distance (l) - The directed distance from initial to final location; Length.
Measured in Meters or feet
units of cm, m, km or inches, feet, yards.
What is displacement?
Displacement (d)- Vector quantity for distance. Right Angles
Calculated (final position – initial position in that direction)
Horizontal and Vertical vectors.
Positive and Negative used for direction.
Why do biomechanists use displacement rather than distance?
Biomechanist’s often use displacement rather than distance because directional information is crucial to calculation of kinematic and kinetic variables.
Skaters distance traveled=?
Skater’s distance traveled = measured from the track left on the ice.
Skaters displacement=?
Skater’s displacement = measured in a straight line from start to finish.
What is speed?
Distance covered over the time interval
How fast an object is moving w/o regard to direction
A scalar quantity
m/s, ft/s, Km/hr, mph
distance
Speed = distance/time = Length/change in time
What is the equation for speed?
s = 𝑙/Δ𝑡
What is velocity?
Velocity (V) – The speed of an object, in a particular direction
V = change in position / change in time
Units are the same as speed but with + or –
Rate of change of displacement - How quickly position is changing in the specific direction.
+ m/s, - ft/s, + mph
What is the equation for velocity?
V = change in displacement/change in time
What is peak rate of motion?
Peak rate of motion: maximum rate of motion achieved
What is average speed/velocity?
Average speed/velocity: speed or velocity divided by the entire interval over which it is measured
What is instantaneous speed/instantaneous velocity?
Instantaneous speed/Instantaneous velocity: the rate of motion at one given instant in time
What is stride length primarily influenced by?
Stride length influenced Primarily by: Body Height
What 6 things is stride length influenced by secondarily?
Muscle fiber composition, Footwear, Level of fatigue, Injury history, Inclination(grade), Stiffness of running surface.
Running Velocity is the product of ____ ____ and ____ ____?
Running Velocity is the product of stride length and stride frequency.
Most regular runners tend to chose a combo of ____ ____ and ____ ____that minimizes the ____ cost of running. Naturally adjusting to their runner’s economy and Oxygen consumption for the given task?
Most regular runners tend to chose a combo of stride length and stride frequency that minimizes the physiological cost of running. Naturally adjusting to their runner’s economy and Oxygen consumption for the given task.
Over-striding puts ____ at risk for injury?
Over-striding puts hamstrings at risk for injury
Elite performers use ____ to manipulate ____ for increased results?
Elite performers use techniques to manipulate variables for increased results
What is acceleration?
change in magnitude and/or direction of the velocity vector with respect to time
The rate of change in linear velocity
What is the equation for acceleration?
change in velocity
Acceleration = change in velocity/time
a = V2-V1/t
In what instances will acceleration be 0, positive, or negative?
Acceleration can be 0:
Velocityfinal = velocityinitial
Acceleration can be positive:
Velocityfinal > velocityinitial
Acceleration can be negative:
Velocityfinal < velocityinitial
Acceleration may be ____, ____, or equal to ____, based on the direction of ____ and the direction of the ____ in velocity.
Acceleration may be positive, negative, or equal to zero, based on the direction of motion and the direction of the change in velocity.
What is average acceleration?
Average acceleration: the rate of change in velocity divided by the entire interval over which it changed
What is instantaneous acceleration?
Instantaneous acceleration: the rate of change in velocity at one specific instant in time
What is linear kinetics + 3 examples?
Kinetics: the study of the forces that inhibit, cause, facilitate, or modify the motion of a body
Forces such as gravity, air resistance and friction
Without forces (____), the spatial and temporal characteristics of motion (____) remain constant.
Without forces (Kinetic), the spatial and temporal characteristics of motion (Kinematics) remain constant.
Newton’s first law?
1st Law: Inertia - A body will maintain a state of rest or constant velocity unless acted on by an external force that changes the state.
Newton’s second law?
2nd Law: Acceleration – Force is equal to the change in momentum per change in time. Force = Mass x Acceleration
Newton’s third law?
3rd Law: Reaction – For every action, there is an equal and opposite reaction
What is the law of gravity?
Law of Gravity - All bodies are attracted to one another with a force proportional to a product of their masses and inversely proportional to the square of the distance between them
What is momentum?
Momentum – A system’s quantity of motion
The greater the ____ ____ ____ possessed by a system, the more difficult it is to stop that motion?
The greater the quantity of motion possessed by a system, the more difficult it is to stop that motion
Momentum can be gained by what?
Momentum (M) can be gained by:
Increasing mass (m): an elephant
Increasing velocity (v): a bullet
Equation for momentum?
So, momentum may be calculated as follows: M = mv
Momentum (M) = mass * velocity
Units : kg* m/s
When is linear momentum most often seen?
Most often seen during a collision due to change in velocity
What is the law of the conservation of momentum?
In the absence of external forces, the total momentum of a given system remain constant
Best way to evaluate conservation of linear momentum is through ____?
Best way to evaluate conservation of linear momentum is through collisions
When evaluating the conservation of linear momentum, what is often ignored?
Often ignore external forces like friction, air resistance and gravity.
What are two types of collisions?
2 types of Collisions
Elastic – Collide and Bounce off
Inelastic – Collide and Stick together
No collision is perfectly elastic or inelastic
What is the equation for an inelastic collisions?
(m1v1i + m2v2i) = (m1+ m2) vf
or
(m1v1i + m2v2i) / (m1+ m2) = vf
What is the equation for an elastic collision?
M1V1 + M2V2 += M1V1 +M2V2
What is impact?
Collision between two objects where a large force is exchanged in a small time interval
Example: All club sports
What are the two types of impact results?
2 types of impact results
Perfectly elastic impact – velocity of object is conserved
Perfectly plastic impact – velocity of object is lost. Object changes shape and does not return to original shape.
If impact lands between perfectly elastic or plastic it has a coefficient of restitution.
0 – 1 coefficient. Closer to 0 = plastic. Closer to 1 = elastic
When two bodies collide there is an exchange of ____?
When two bodies collide there is an exchange of forces
The difference in velocities between 2 objects immediately post impact is proportional to????
The difference in velocities between 2 objects immediately post impact is proportional to the difference in their velocities immediately before impact.
What is the equation for the cofficient of restitution?
-e = relative velocity after impact / relative velocity before impact
-e = v1 - v2 / u1 - u2
e = sqrt (height of rebound / height of drop)
What is impulse?
The Product of applied force acting over a time interval
Impulse = Force*time
Truly is a change in a systems total momentum
We can assume then that Impulse and Momentum are related.
F= (mv)2 – (mv)1 F = Δ M
What is the equation for impulse?
Impulse = Force*time
change M = change F (change t)
What is work?
Work – performed when an object is displaced by a force
Mechanical context, force multiplied by the displacement of the resistance in the direction of the force.
What is energy?
Energy – the capacity to perform that work
Work is an energy transfer
What is the equation for work?
W = Fd 1J = 1Nm
An isometric action does ____ do mechanical work?
An isometric action does NOT do mechanical work.
Concentric contraction is what kind of work?
Positive work
Eccentric contraction is what kind of work?
Negative work
Effort is not to be confused with ____?
Work
What is power?
Power – the amount of mechanical work performed at a given interval
The RATE of doing work
Equation for power?
P = Work / time
Units of Watts (1 Joule/ sec)
Horsepower (1Hp= 746W)
Power is greater if the same amount of ____ is performed in a ____ time frame?
Power is greater if the same amount of work is performed in a shorter time frame
What is energy?
The capacity to do work
What is potential energy?
Potential Energy (PE) – the capacity of an object to perform work because of its position, deformation, or configuration
What is the equation for potential energy?
PE = wt * h or PE = mag h
Stored energy
The weight of a body is typically fixed so changes in PE are usually based on height.
What is GPE and its equation?
Gravitational potential energy: GPE = wt x h
What is elastic potential energy also called?
Elastic Potential Energy – Strain Energy
What is strain energy?
Strain Energy – Letting the deformation of a body and its return to original shape produce work.
What is the equation for strain energy?
SE = 1⁄2k Δx2
(ie. Achilles tendon)
Elastic potential energy:
SE = strain energy (energy due to deformation)
k = stiffness (spring) constant
Δx2 = deformation (or change in length) of the object
What is another name for strain energy?
Elastic potential energy
What is KE?
Kinetic Energy (KE) – the energy of motion
What is the equation for KE?
KE = ½ mv2
Motionless means v = 0 so KE = 0
Velocity makes KE very dynamic bc its squared
What is the law of conservation of mechanical energy?
Law of Conservation of Energy – Energy cannot be created or destroyed. It is just transferred from one from to another.
Mechanical energy is conserved.
Energy transfer from one system to another takes place in the form of work.
What is the principle of work energy?
The work performed by externally applied forces other than gravity causes a change in energy of the object acted upon.
What is another equation for work?
Work = the change in energy that is produced in the object acted on.
W = ΔKE + Δ PE + Δ TE
TE = thermal Heat
How can injuries be reduced using biomechanics?
Reducing injuries by spreading out force over an area or time.
Padding, helmets, boxing gloves, turf, Airbags, catchers glove, shoe
What is pedagogy in linear kinematics?
Pedagogy – teaching strategies for applying force more efficiently
What is adapted physical education?
Adapted PE – Changing the equipment for success
How can motor learning be used in force production?
Motor learning – application of force for efficient practice and play
Throwing, kicking, striking objects, controlling the kinetic chain
What sports use collisions?
Sport Science – Tactical use of collision in games
Curling, shuffle board, Bocce ball, billiards, bowling
