Chapter 12,13,14,15
Contact is influenced by the
-weight, radius, and deformation of the rolling object -coefficient of friction between the two surfaces
scissors, crowbar is what type of lever class
1st (FAR)
Type of form drag 1
Laminar flow: smooth, parallel pattern of movement
Coefficient of Restitution (COR)
Measure of bounciness or resilience -COR e=√bounce ht/ drop ht -highest COR is 1 and lowest 0
Torque (angular rotation )
Rotary effect of a force about an axis or rotation Measure as the product of force and forces moment arm
Three types of drags
Surface, form and wave drag
relative velocity
The difference between the objects absolute velocity and the fluids absolute velocity
What happens when angular momentum is conserved?
changes in body configuration produce a trade-off between moment of inertia and angular velocity, with a tuck position producing greater angular velocity
Energy
the ability to do work
Newton's 1st Law
(Law of Inertia) an object in motion tends to stay in motion & an object at rest stays at rest unless acted upon by an outside force. The resultant of external forces acting on it is 0
cat twist
- Can be initiated with ZERO angular momentum - Must be flexed at waist - Twist by rotating one part of the body that has reduced rotary inertia against another which has higher rotary inertia
Kinetic energy is used to what?
-Do the work in collision -cause the deformation of bodies -generates heat and noise (occurs in all collisions)
What is the principle of conservation of angular momentum
-When gravity is the only acting external force, angular momentum is conserved -The total angular momentum of a given system remains constant in the absence of external torques
Wheelbarrow is what type of lever class
2nd (ARF)
Lifting something, rowing
3rd (AFR)
Fluid Mechanics
A branch of mechanics dealing with the properties and behavior of liquids and gases. Fluid flow around the athlete or object. Forces create by this flow can produce, drag , lift, buoyancy and spin.
Static equilibrium
A motionless state in which there is no net force or net torque acting.
Newton's 3rd Law
Law of Action-reaction. For every action there is an equal and opposite reaction (torque and or force)
a lift force caused by a spin is called a
Magnus force (Gustav magnus 1852)
Momentum and kinetic energy
Newtons 3rd law. Directly proportional to mass. Increases to square of velocity Mass constant and double velocity, KE increases fourfold - Triple velocity and KE increases nine-fold
Buoyancy with air
Object filled with air less dense than surrounding fluid
wave drag
Occurs at interface between wave and air. Increases according to cube of the velocity.
Power
P=W/t, measured in Watts(metrics) Power vs strength Example: 2 lifters of same mass lifting same weight Lifter A moves weight in one second ( worked quickly) Lifter B moves weight in two second Both move weight same distance but less time for A
µs
Parallel to contact surfaces
R
Perpendicular to contact surfaces
Archimedes' Principle
Physical law stating that the buoyant force acting on a body is equal to the weight of the fluid displaced by the body Fb= Vdr
Stability
Resistance to disturbance of balance -athletes increases or decrease stability according to requirements of skills they preform. -greater stability greater resistance
Buoyant forces other factors : type of water
Salt water—> more dense —> more floatation Fresh water —> less dense —> less floatation
Strain energy (SE)
Stored energy that results from an object being pushed out of original shape and then restore itself to original (resting) shape. -SE=½ kx 2 K=stiffness of object - X=deformation of object from original
Gravitational potential energy (PE)
Stored energy which results from acceleration of gravity PE= Wh= mgh (joules)
moment of inertia formula
Sum of products of each particles mass and the radius of rotation I = Emr^2
Balance
The ability to control the forces that make an athlete stable
Factor that influences angular momentum is
The distribution of mass with respect to the axis of rotation . Angular momentum is proportional to the square of the radius of gyration.
line of buoyancy vs line of gravity
The line of action of buoyant force is through the center of volume (where the center of the buoyant force concentrates its upward thrust) - Center of gravity of the displaced water • The line of action of gravity is through the center of mass
Cyclists abs runners lean into a curve to offset what
Torque created by centripetal force acting on the base of support
Type of form drag 2
Turbulent flow: chaotic flow pattern. Characterized by more turbulent and multidirectional fluid movement
Elastic collisions
Two bodies hit center. Formula: mA uA + mB uB = mA vA + mB vB -momentum and KE conserved (perfectly elastic)
The bends
Up too quickly. diver crippled and bent over
Buoyant forces other factors : temperature of water
Warmer water—> less density —> more floatation Colder water —> more dense—> more floatation
Hydrostatic pressure in h20
Water more dense then air 800 times more Pressure increase in depth 1 atmosphere = 14.7 psi 10m depth= (14.7 x2)= 29.4 psi 20m depth = 14.7x 3 = 44.1 psi 30m depth=14x4 = 58.8 psi
Momentum and kinetic energy
What is conserved in a completely elastic collision
Slide-Spin
Will Catawba a ball to swerve to the right or left. Example table tennis
Backspin
Will Keep a ball aloft longer. Example: gold clubs
Topspin
Will cause a ball to drop earlier example soccer players use it for corner kicks or penalty to swerve
Newtons laws specifically state that
You can not initiate rotation without an external torque being applied on it. A car cab initiate rotation while airborne
lever
a simple machine that consists of a rigid bar like body that can be made to rotate about an axis of a fulcrum
dynamic equilibrium
a state of balance between continuing processes
Law of Gravitation
all bodies are attracted to one another with a force proportional to the product of their masses and inversely proportional to the distance between them
kinetic friction (fk)
constant magnitude friction generated between two surfaces in contact during motion fk=µkR
Work
force x displacement Displacement= change in position
rolling friction
friction that occurs when an object rolls over a surface. Slightly deformed during contact Influenced by weight, radius and deformation of the rolling object. Coefficient of friction between the two surfaces
sliding friction
friction that occurs when one solid surface slides over another
moment of inertia
inertial property for rotating bodies representing resistance to angular acceleration; based on both mass and the distance the mass is distributed from the axis of rotation
Newton 2nd law
law of acceleration The change of motion of an object is proportional to the force applied , and is made in the direction of the straight line in which the force is applied.
inelastic collision
mA uA + mB uB = (mA + mB) v Momentum conserved but KE not conserved
What is angular momentum?
quantity of angular motion possessed by a body; measured as the product of moment of inertia and angular velocity H=IW As mass or angular velocity increases, angular momentum increases proportionally.
Power
the rate at which work is done p=w/change t
mechanical advantage
the ratio of moment arm of force to the moment arm of the resistance of resistance arm for a given lever
centripetal force formula
Fc=mv^2/r or fc=mrw^2
Friction
Force acting over the area of contact between two surfaces in the direction opposite that of motion or motion tendency
lift
Force acting perpendicular to motion that deflects an object from its original pathway.
centripetal force
Force directed toward the center of rotation for a body in rotational motion
buoyancy
Force opposing gravity acting on object partially or fully immersed in liquid or gas
Drag
Force opposing motion through a fluid
static friction (µs)
Friction that acts on objects that are not moving Fm =µsR
atmospheric pressure
Gravity's pull on the atmosphere. Greatest pressure at sea level less at altitude. 14.1 psi
Hydrotastic pressure in h2O divers
Air regulator balance air pressure in their lungs with that of the oceans depth. At 10m air is reduced to ½ that at surface At 20m air is reduced to 1/3 that of surface At 30m air is reduced to ¼ that of surface volume
form drag (shape drag)
Also called shape or pressure drag. Sun if the impact forces resulting from the collisions between the fluid molecules and surface of object. Increases according to square of the velocity max by roughness of the object especially at low velocities
Surface drag (skin friction)
Also called skin friction or viscous drag amount deter,index by relative velocity, area of surface, roughness of objects, fluids viscosity
Stability determining factors
Base of Support • Central line of gravity within base of support • Center of Gravity • Body Mass • Extension of base in direction of oncoming force • Shift line of gravity towards line of force
Kinetic energy (KE)
Capacity of doing mechanical work by moving KE= ½ mv 2 (unit) Joules
Swimmers position their center of gravity where
Close to the front of their bases of support to prepare for forward acceleration
Magnitude of the friction is the product of what?
Coefficient of friction (µs) and normal contact force (R)
A skater has a tendency to continue gliding with
Constant speed and direction bc inertia
center of gravity
Crouching down increases stability
Magnus effect
Deviation in the trajectory of a spinning object toward the direction of spin
nitrogen narcosis
Down too low. High concentrations in blood due to extreme depth
hydrotatic pressure
Exerted by the wt of a fluid. Related to buoyancy. Pressure-force per unit area
Buoyancy of water
Extension of hydrostatic pressure. Greater pressure with depth—> more powerful upward force pushing on object from below
Bernoulli's Principle (Daniel Bernoulli 1738)
Faster moving fluids exert less pressure laterally than do slower moving fluids
