How Does a Glass Fibre Flywheel Store Kinetic Energy in Buses?

• Katy96
In summary: You should have a formula for the number of radians in a revolution. You should also be able to convert minutes to seconds. You should also be able to look up the formula for angular velocity. You have all the information you need to answer this question.In summary, a flywheel made of glass fibre has been developed by BP to store the kinetic energy of buses when they come to a bus stop. The maximum energy stored in the flywheel is equivalent to the energy lost by a 16,000 kg bus braking from 48 km when it comes to rest. The bulk of the flywheel’s mass is in its rim which moves at 1300 km when the flywheel rotates at the maximum angular velocity of
Katy96 said:
when I did that I got the right answer so in part c do I use vmax=rωmax or do I use I=0.606mr2

Does that give the right answer?

I'm going offline now. Good luck with the rest of it.

PeroK said:
Does that give the right answer?

I'm going offline now. Good luck with the rest of it.
thanks.

Its just part e I'm struggling on now

Katy96 said:
e) Determine also the

Katy96 said:
Its just part e I'm struggling on now
Yes. It is quite the conundrum.

jbriggs444 said:
Yes. It is quite the conundrum.
sorry it meant to say Determine also the mean frictional torque causing the slowing down in the two minute stop.

You know how much energy it had at the beginning of the two minute stop. You have already used that to calculate its angular velocity at that time.

The question tells you what fraction of the starting energy it has at the end of the two minute stop. How much energy is that? How fast does that mean that it must be rotating at the end of the two minutes?

this is what I know, i need to use the change in the KE to find the final angular speed, and hence the angular deceleration, using the equations of angular motion and torque Important to show answer is negative, as result of deceleration
The force providing the centripetal acceleration acts towards the axis so cannot have a torque about it.and flywheel does not stop during the 2 mins.

Katy96 said:
this is what I know, i need to use the change in the KE to find the final angular speed
Then there is a starting point. What is the change in KE?

jbriggs444 said:
Then there is a starting point. What is the change in KE?
that's where I get stuck

The problem statement says that four fifths of the flywheel's energy remains after two minutes.

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