Work, Torque, and Power Flashcards

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1
Q

a couple

A

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

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2
Q

torque

A

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

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3
Q

function of a flywheel

A

store energy

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4
Q

how does a flywheel work>

A
  • 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
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5
Q

what is rotational KE related to

A

moment of inertia and the quare of the angular speed

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6
Q

how do you increase the energy a flywheel can store?

A
  • 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
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7
Q

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

A
  • become impractical
  • too large and heavy
  • angular speed to high, and centrifrugal force can cause the flywheel to break apart
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8
Q

why are modern flywheel made out of carbon fibre

A

despite being lighter they can be spun faster

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9
Q

what causes friction in flywheels, how is it reduced?

A
  • 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
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10
Q

How do flywheels smooth torque and angular velocity

when is this used

A
  • 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
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11
Q

where are flywheels used?

A
  • 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
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12
Q

what are the advatages of flywheels

A
  • efficient
  • last long time
  • recharge time is short
  • they can react and discharge quickly
  • environmentally friendly
    • dont rely on chemical
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13
Q

disadvantages of flywheels

A
  • 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
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