Work, Torque, and Power Flashcards Preview

a2 physics engineering > Work, Torque, and Power > Flashcards

Flashcards in Work, Torque, and Power Deck (13)
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1

a couple

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

2

torque

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

 

 

 

3

function of a flywheel 

store energy

4

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

 

 

5

what is rotational KE related to 

moment of inertia and the quare of the angular speed

6

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

 

 

7

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

 

 

8

why are modern flywheel made out of carbon fibre

despite being lighter they can be spun faster

 

 

 

9

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

 

 

 

10

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

 

 

11

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

 

 

12

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

 

13

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