Dynamics and muscle contraction Flashcards
What does dynamics study?
The relationship between the motion of bodies and the causes (forces) that generate it
What is newtons first law?
That if a body is at rest or at moving at a constant speed in a straight line it will remain at rest or keep moving in a straight line at a constant speed unless acted upon
2 different name for Newtons first law
1st principle of dynamics
Principle of inertia
What is newtons second law?
The acceleration of an object is dependent on 2 variables:
The net force acting upon the object
The mass of the object
How are F and a proportional?
Directly
How are m and a proportional?
Inversely
What is center of mass (COM)?
The point in a system that responds to external forces as if the total mass of the system were concentrated at this point
Mean position of the mass in an object
What is the center of gravity (COG)?
The point where the mass of the body is concentrated
When are COM and COG the same?
When the gravitational field is uniform across an object
What 3 things can forces do?
Impart an acceleration to a body free to move
Deform a constrained body
Rotate a body around a point (torque) if force is applied to a point of rotation
What does the centripetal force cause?
The tendency to move towards the centre
What does the centrifugal force cause?
The tendency to move straight without turning
What force do we feel when a car is turning?
The centrifugal force
What kind of force is centrifugal force?
An apparent force, it is not real
What kind of proportionality is there between the deformation and force applied?
Linear
2 ways to measure forces
Statically or dynamically
What kind of quantity is force?
Derived
What is the difference between the Kg weight and the mass?
Mass is constant, Kg weight depends on force
What is the relative density?
The ratio between the mass of a certain volume of a substance and the mass of an equal volume of distilled water at 4c*
What is the absolute density?
Ratio between the mass of a body and its volume
What is the relative specific weight?
Ratio of weight of a body and weight of an equal volume of distilled water at 4c*
What is the absolute specific weight?
Ratio between weight of a body and its volume
What is the torque?
The vectorial product of 2 vectors
What is Newton’s third law?
For every action force in nature there is an opposite and equal reaction
What symbol defines momentum?
q
Equation of momentum
q=m • v
What is the electrostatic force defined by?
Coloumbs law
What is the columb derived from?
Ampere
What are the 2 properties of matter?
Charge
Mass
Formula for centripetal acceleration
v^2/r
What is restoring force in SHM?
Force that brings the body back to the center of oscillation
What composition does fast animals tend to have?
Long, light limbs and powerful muscles
How do you change m/s into km/h?
Multiply by 3.6
What is the speed of the animal directly proportional to?
Muscle strength
The extent of the contraction
What do muscles convert chemical energy into?
Mechanical work
What is the efficiency of muscle always?
Less than 100%
2 types of muscle contraction
Isotonic
Isometric
What is isotonic muscle contraction?
When muscle is performing work against an external force (shortens or stretches)
What is isometric muscle contraction?
When muscle contracts to balance and external force but neither lengthens or shortens
What happens during isometric contraction?
Muscle doesn’t shorten
Sarcomeres shorten (generating force)
Elastic elements stretch, allowing length of muscle not to vary
What happens during isotonic contraction?
Sarcomeres shorten more
Elastic elements are already stretched so entire muscle shortens
When is the tension force (T) maximum during isometric contraction?
When length (L) of muscle is equal to that at rest (L0)
What happens when the muscle is shorter or more stretched during isometric contraction than in the resting position?
It developed less strength
At resting length, is the passive tension of a muscle 0?
No
What happens if we cut the tendon of the muscle at resting tension?
It would get 20% shorter
What does the shortening change in length (^L) depend on in isotonic contraction?
The load
When is the shortening ^L in isotonic contraction equal to 0?
When maximum force (tension), Max is equal to the external load (F)
Tmax=Fmax
When is the shortening ^L in isotonic contraction its maximum?
When the load is 0
What kind of graph does the defence of the shortening on the load make?
A linear graph
What is the external load (F) equal to during isotonic contraction when the work and power produced are maximum?
F=1/2*Fmax
What is the absorbed power of muscles
Energy consumed in the unit of time
What is the power produced in muscles?
Useful work in the unit time
How many joules is 1 calorie?
1 cal = 4.184 J
