Work, Torque, and Power Flashcards Preview

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Flashcards in Work, Torque, and Power Deck (13)
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a couple

pair of forces which cause no resultant linear motion, but which cause an object to turn



when a force (or couple) causes an object to turn, the turning effect is known as torque





function of a flywheel 

store energy


how does a flywheel work>

  • heavu wheel with a high mopement of inertia to resist changes to its rotational motion
  • once is is spinning its hard to make it stop spinning, 
    • high angular moment
  • turns torque into rotational kinetic energy
  • energy continuously put in two overcome frictional torque
  • when extra energy is needed in the machine, the flywheel decelerates transferring some of its kinetic enrgy to another part of the machine




what is rotational KE related to 

moment of inertia and the quare of the angular speed


how do you increase the energy a flywheel can store?

  • heavier 
    • moment of inetertia, and so KE stores, is directly proportional to the mass, heavier the flywheel the better
  • faster
    • energy stored increases with agnular speed squred
  • spoked
    • compared to a solid wheel, a spoked wheel of the same mass stores almpost twice as much energy




WHat are the limitations when increases the factor to increase KE store

  • become impractical
  • too large and heavy
  • angular speed to high, and centrifrugal force can cause the flywheel to break apart




why are modern flywheel made out of carbon fibre

despite being lighter they can be spun faster





what causes friction in flywheels, how is it reduced?

  • causes
    • air resistance
    • friction between the wheel and bearings
  • lubricated
    • reduce friction
  • levitated with superconduction magnets
    • no contact
  • operated in vacuums or sealed contiainers to reduce drag





How do flywheels smooth torque and angular velocity


when is this used

  • force supplied vary, flywheels used to keep angular velocity of any rotating components constant
  • flywheels each use power to charge up, then they delivered the stored energy smoothly to the rest of the system, instead of bursts
  • used when the force that the system has to exert can vary
    • if load torque is too high then the flywheel decelerates
  • when the engine torque is higher than the load toruqe, the flywheel accelerates anstores the spare energy




where are flywheels used?

  • potters wheel 
    • used to keep speed of wheel constant
  • regenerative breaking
    • flywheel charges up with the energy being lost. when the vehicle accelerates, teh flywheel uses its energy to turn the vehicles wheels faster




what are the advatages of flywheels

  • efficient
  • last long time 
  • recharge time is short
  • they can react and discharge quickly
  • environmentally friendly
    • dont rely on chemical



disadvantages of flywheels

  • much larger ad heavier than other storage methods
  • safety risk as the wheel could break apart at high speeds
    • protective casing to prevent this results in etra weight
  • energy lost through friction
  • if used in moving objects, they can oppose changes in direction. which can cause problems for vehicles