Lectures 12-18 Flashcards
Slide 6, lecture 12
To show which way makes radians positive and which way makes radians negative
Equation for angular displacement
Angular displacement = final angle - initial angle
Equation for angular velocity
Angular velocity = angular displacement / change in time
Equation for angular acceleration
Angular acceleration = change in angular velocity / change in time
Equation for linear velocity
Linear velocity = angular velocity x radius
Recap lecture 12 bit about radians
DO NOT SAVE THIS TILL NIGHT BEFORE IT IS VERY IMPORTANT
What is an ”open chain”? (Recap, Slide 17, lecture 12)
Where the distal segment (hand or foot) is free to move in space. Movements occur distal to the moving joint
What is a “closed kinetic chain”? (Recap Slide 18, lecture 12)
Where the distal segment (hand or foot) is fixed to a solid surface
Equation for angular displacement
Angular displacement = final angle - initial angle
Equation for angular velocity
Angular velocity = angular displacement / change in time
Equation for angular acceleration
Angular acceleration = change in angular velocity / change in time
What is the linear to angular analogue of mass? (Look is what this means)
Moment of inertia
What is the linear to angular analogue of force? (Look is what this means)
Torque (moment of force)
What is the linear to angular analogue of momentum? (Look is what this means)
Angular momentum
What is the linear to angular analogue of Newton’s laws? (Look is what this means)
Newton’s laws (angular analogues)
Equation for moment of inertia
Moment of inertia = mass of each particle x squared distance from axis of rotation
Heavier objects or those with mass distributed away from their axis of rotation are…? (Related to moment of inertia)
Harder to move and difficult to stop
What is torque?
It is an “angular force”
It is also a vector (has a magnitude and direction
Look at slide 11
Lecture 13, torque
Equation for torque
Torque = Force x Moment arm
What is torque measured in?
Nm
Find units for all equations
On lectures
Do equation practice with help from recap
Slide 20 - 24, lecture 13
What is the moment arm?
The shortest perpendicular distance from a force’s line of action to the axis of rotation
How to measure torque
Slide 5-8, lecture 14
Slides 9-10
Calculating equilibrium
Lever systems, F L E = ???
1 2 3
Example of a first class lever system?
Elbow extension against a resistance
Example of a second class lever system?
Calf raise
Example of a third class lever system?
Bicep curl
What is an advantage of a second class lever system?
The effort arm is greater than the load arm. So a large load can be moved with a relatively small effort
What is the problem with the mechanical advantage of the second class lever?
It means that there is a reduced range of motion (less movement)
What is the mechanical disadvantage of a third class lever system?
The load arm is greater than the effort arm - so it takes a larger effort to lift a relatively small load
What is a benefit of the mechanical disadvantage of a third class lever?
It allows for a greater range of motion (more movement)
Equation for (tangential) linear velocity?
(Tangential) Linear velocity = angular velocity x radius
Centripetal forces
Slide 5, lecture 15, what are the symbols in the equations
Slides 13 - 18, recap (centripetal and centrifugal forces)
Lecture 15
So equation practice throughout all lectures
Lecture 12-18
What is an isometric contraction?
A muscular contraction where the length of the muscle stay the same
What is an isotonic contraction?
A muscular contraction where the length of the muscle changes
What is an isokinetic muscular contraction?
A muscular contraction with the same angular velocity
What is a concentric muscular contraction?
One where the length of the muscle shortens
What is an eccentric muscular contraction?
One where the length of the muscle lengthens (becomes longer)
A downwards movement is normally what type of muscular contraction?
An eccentric one
Recap lecture 16
One of the ones you missed
Recap lecture 15
One of the ones you missed
Newton’s first law of motion
The law of inertia
A body continues in a state of rest or uniform velocity unless acted upon by an external or unbalanced force
The angular equivalent of Newton’s first law of motion
A rotating body will continue to rotate about its axis of rotation with a constant angular momentum unless acted on by an external torque
Recap what symbols mean
Slide 4, lecture 17
Learn conservation of angular momentum
PE book, page 98, slide 6, lecture 17
Newton’s second law of motion
Law of acceleration
A body’s rate of change of momentum is proportional to the force applied to it and it acts in the direction of that force
The angular equivalent of Newton’s second law of motion
The rate of change of angular momentum is proportional to the torque chasing it
Newton’s third law of motion
The law of reaction
For every action there is an equal and opposite reaction
Angular equivalent of Newton’s third law of motion
For every torque exerted by a body on another, there is an equal and opposite torque exerted
Equations for Newton’s laws of motion and the angular equivalents
Throughout lecture 17
Recap lecture 18
No pp slides
Definition of moment arm
The moment arm is the shortest perpendicular distance from a force’s line of action to the axis of rotation
How do you convert radians to degrees? (Smaller to bigger number)
Multiply by 360/2pie
How do you convert degrees to radians? (Bigger to smaller number)
Multiply by 2pie/360
How many radians are there in every circle?
2pie radians
Centripetal (radial) acceleration equation
Tangential (linear) velocity squared / radius
What is the unit for centripetal (radial) acceleration?
Radians/second
Equation for centripetal force
Mass x tangential (linear) velocity squared / radius
What does pennation allow for?
Allows more muscle fibres in the muscle, which are able to contribute to producing more force
If you want to move something quickly, what type of muscle fibres do you want?
Longer
What type of muscle giver do you want in order to produce a lot of force?
Shorter and greater physiological cross sectional area
How many degrees are in one radian?
57.3 degrees
Density equation
Density = mass/volume
Does the density of an object have to be higher/lower than the object it is floating in to sink
Higher
What is the equation for angular momentum?
Angular momentum = moment of inertia x angular velocity
Equation for torque in terms of law of reaction
Ta = -Tb
In terms of the force velocity curve, at what point is maximum power achieved?
1/3 of maximum velocity
What does a force through the CoM result in, in terms of rotation
No rotation
What does a force applied around the CoM result in, in terms of rotation
Rotation and linear motion
What does a force couple result in, in terms of rotation
Pure rotation
What type of turning force is an eccentric/off-centre one?
One where force is applied around the CoM
What is a centrifugal force?
It is an outward acting force
Equal and opposite to centripetal force
Reaction to the centripetal force
What is a centripetal force?
A force that acts on a body moving in a circular path and is directed to the centre
Define conservation of angular momentum
Angular momentum is a conserved quantity which remains constant unless an external eccentric force or torque is applied
Are you more likely to sink or float in a very dense fluid?
Float
Are you more likely to sink or float in a fluid that is not very dense?
Sink
Definition of a radian
A unit of measurement of angles, equal to about 57.3 degrees
