Torques, Angular Kinetics/Kinematics Flashcards
Since producing torque requires force, there just be: (3)
Magnitude (how much)
Direction (linear and line of action)
Point of application
How to create more torque (without changing force):
Move “hand farther away from axis = inc moment arm
T= F*r
r = moment arm
The _______ the moment arm the greater the _______.
Longer/ greater
Torque
When forces are the _______ with a ______ moment arm = ____ _____
Same
Long
Greater torque
When is the moment arm the longest in the human body (muscle and joint systems?
90 degrees
- extend slightly- attachment moves closer to axis = moment arm shorter – same with < 90dg
What determines the amount of torus we generate?
Moment arm length Muscular force (strength of contraction) Position/angle of the joint
Longer radius =
Greater velocity for any given angle
S=wr = change in angle / t
Longer club =
Greater linear velocity = greater displacement
Components of Angular Acceleration
Tangential
Centripetal
The Moment of Inertia equation applies best to:
Objects in which distribution of mass is constant through the rotation
Can angular moment be changed after leaving the ground?
No, but angular velocity can change (rotate faster = dec moment of inertia
Angular Momentum: changes in linear motion
Rigid and Non-Rigid
- Rigid object: generally depends on change in angular velocity (w)
- Non-Rigid: easily influenced by changes in avg. velocity (w) OR the moment of inertia (I)
Why does Newton’s 1st not require the angular velocity to remain constant?
change in angular velocity countered by change in moment of inertia
- H~= (dec) I * (inc) w
The _______ the object is immersed the ______ the ______.
Deeper submerged
Greater
Pressure
What is the name for when the buoyant force is equal to the weight of the displaced fluid?
Archimedes Principle
How does temperature effect the SG water?
high temp = dec SG (molecules farther apart)
Cold temps = inc SG (molecules closer together)
When will an object float?
When an object has SG less than water
- will weight less than an equal volume of water
When will an object sink?
When an object has a SG greater than water
- weight more than an equal volume of water
What are the two components that determine if an object will float or sink?
Density
Specific Gravity
What is a dynamic fluid force dependent on?
Density of fluid
SA of the object
Relative Velocity of the object to the fluid
What are the 2 major components of dynamic fluid force?
Drag
Lift
What are the 2 types of drag forces?
Surface
Form
Surface Drag- Cd is influenced by:
- Roughness of the object surface
2. Fluid viscosity (friction btw fluid layers)
Form Drag- Cd is influenced by:
- Objects shape
2. Surface texture
How do you reduce drag? (4)
- Make body surface/ clothing smoother
- Streamline shape
- Reduce SA exposed to flow
- Perform at: high altitude, in warm water, draft, run with wind
How does lift work on an airfoil?
- flow across the top is faster than the bottom
- creates L pressure on top and H pressure on bottom
- pressure travels H –> L
How does the Magnus Effect work?
- H pressure builds on the surface that is spinning against the flow
- L pressure on surface spinning “with” the flow (less resistance to flow)
- object moves toward L pressure
How does Bernoulli’s Principle work?
- L pressure created on top ( fast moving fluids = L pressure)
- H created on the bottom
- H –> L
Relationship btw Angular and Linear Velocity
avg linear speed of a point on a rotating obj
avg angular velocity of the object times the radius
Angular Interpretation of Newton’s 1st
- angular momentum remains constant unless acted on by an external force
(remains in rotational motion unless acted upon)
Angular Interpretation of Newton’s 2nd
- net torque produces angular accel proportional to:
1. Torque (magnitude) in the
2. Direction of the torque and
3. Inversely proportional to the Moment of Inertia
Angular Impulse and Momentum Relationship
- same as linear
- ang impulse = ang momentum.
- inc torque OR the time a torus is applied = inc ang momentum
Angular Interpretation of Newton’s 3rd
For every torque exerted by one obj on another, there is an equal (magnitude) and opposite (direction) torque exerted by the 2nd obj on the 1st
- 2 obj share the same axis
Eccentric Force
- an external force not direct through an objects CoG
- torque
- linear and ang motion
Centric Force
- an external force directed through an objects CoG
- NO torque
- linear motion only
Laminar Flow
Fluid molecules stay close to the obj surface
Angular Motion
When all points on an object move in circular paths about the same axis (do NOT travel the save distance)
- angle formed by 2 lines/planes or one line and one plane intersecting
Centripetal Acceleration
Linear accel directed toward the axis of rotation
Bernoulli’s Principle
Fast moving fluid exerts less pressure than slow moving fluids
Lift Force
- Dynamic fluid force
- acts PERPENDICULAR to the relative motion of the object (with respect to fluid)
- not always upward (spoiler)
- often generated when the obj is longer in the dimension // to the flow
Tangential Acceleration
The component of linear accel tangent to the circular oath of a rotating object
- occurs even if the object continues to rotate about its axis
Archimedes Principle
The size of the buoyant for is equal to the weight of the fluid displaced by an object
Drag Force
- dynamic fluid force
- acts in OPPOSITION to the relative motion of the object (with respect to fluid)
- tends to slow the object if it’s the only force acting
Relative Angular Position
Both lines/planes can move
- elbow: forearm and upper arm can move
Absolute Angular Motion
One line/plane is fixed
- elbow- move forearm, keep upper arm still = bicep curl
Torque: Pulling at an angle (same amount of force)
Can pull with same amount of force and SHORTEN the moment arm
What is the Magnus Effect?
A lift force created by the SPIN of an object
Dynamic Fluid Force
- forces exerted on an object as it moves through a fluid and/or as a fluid moves past the object
- dependent on:
1. Density of fluid
2. SA of object
3. Relative velocity of the object to the fluid
2nd Class Levers
Wheelbarrow
Nutcracker (metal)
Human Body- ball of foot (a), plantar flexors (F), body aligned over tibia (R) _a____ ⬇️R____⬆️F
Buoyant Fluid Forces
- forces due to immersion
- acts upward (vertical) on an object immersed in fluid
Specific Gavity
The ratio of the weight of an object to the weight of an equal volume of water
Weight obj/weight H2O
Surface Drag
Caused by the friction btw an object’s surface and the fluid it’s moving through
- roughness
- fluid viscosity
- skin friction
Form Drag
Related to type of flow: laminar or turbulent
- ⬆️ with turbulent flow
- influenced by- object shape and surface texture
Moment of Inertia
- quantity of angular inertia
- dependent on:
1. Distribution of amass
2. Axis of rotation - when smaller (mass closer to axis) = ⬆️ angular velocity/accel
Torque
- a turning/ rotary effect produced by force
- product of Force and the perpendicular distance from the line of faction of the force to the axis of rotation
- result of an OFF AXIS FORCE causing a turning effect
3rd Class Levers
- rowing (upper hand)
- human muscle and joint systems
- most levers within the human body
a____⬆️F____⬇️R
Pressure
- buoyant force per unit area (N/m2)
- acts in all directions on immersed obj
- ⬆️ linearly with depth
Radius of Gyration
- represents an obj’s mass distribution relative to the axis
- changes if:
The axis of rotation changes
Distribution of mass about the axis changes
Moment Arm
Shortest distance from axis of rotation to the line of action of the force
- always perpendicular to the line of caption (right angle)
1st Class Levers
Seesaw ⬇️F_____a______⬇️R
Scissors
Lever to move heavy objects
Nodding head- atlas vertebrae ( F= m contraction, R= weight of head)
Angular Momentum if the Human Body
The sum of the angular momenta of ALL the BODY SEGMENTS
- approximates the overall momentum of the body
Turbulent Flow
Fluid molecules flow away from the object’s surface- may create a vacuum (L pressure)
Force Couple/Couple
- a pair of non-colinear external forces, EQUAL in MAGNITUDE but OPPOSITE in DIRECTION
- torque
- angular motion only
Relative Velocity
The difference btw an objects velocity and fluid velocity
