A passenger bus in Zurich, Switzerland derived its motive power from the energy stored in a large flywheel. The wheel was brought up to speed periodically, when the bus stopped at a station, by an electric motor, which could then be attached to the electric power lines. The flywheel was a solid cylinder with a mass of 1070 kg and a diameter of 1.70 m ; its top angular speed was 2970 rev/min . 1. At this angular speed, what is the kinetic energy of the flywheel? 2. If the average power required to operate the bus is 1.89

Respuesta :

Answer:

18695271.3209 J

989.167794757 s

Explanation:

r = Radius = [tex]\dfrac{1.7}{2}=0.85\ m[/tex]

N = 2970 rpm

m = Mass of flywheel = 1070 kg

P = Power = [tex]1.89\times 10^4\ W[/tex]

Moment of inertia

[tex]I=\dfrac{1}{2}mr^2\\\Rightarrow I=\dfrac{1}{2}1070\times 0.85^2\\\Rightarrow I=386.5375\ kgm^2[/tex]

Angular speed

[tex]\omega=2970\times \dfrac{2\pi}{60}\\\Rightarrow \omega=311.017672705\ rad/s[/tex]

Kinetic energy

[tex]K=\dfrac{1}{2}I\omega^2\\\Rightarrow K=\dfrac{1}{2}386.5375\times 311.017672705^2\\\Rightarrow K=18695271.3209\ J[/tex]

The kinetic energy is 18695271.3209 J

Time is given by

[tex]t=\dfrac{E}{P}\\\Rightarrow t=\dfrac{18695271.3209}{1.89\times 10^4}\\\Rightarrow t=989.167794757\ s[/tex]

The time taken is 989.167794757 s

The kinetic energy and time would be denoted as follows:

1). [tex]18695271.32 J[/tex]

2). [tex]989.16s[/tex]

Find the kinetic energy

1). Given that,

Mass that the cylinder has = 1070 Kg

Diameter = 1.70 m

Radius

[tex]= 1.70/2 \\= 0.85m[/tex]

Also,

Angular speed = 2970 rev/min

v = 2970 × 2π/60

[tex]= 311.01 rad/s[/tex]

Now, we need to find kinetic energy,

K.E. [tex]= 1/2 m v^2[/tex]

by putting the values,

= 1/2 × 386.53 ×311.01

= 18695271.32 J

b). Given,

Average power to run the bus = 1.89m

[tex]Time = E/p[/tex]

[tex]= 18695271.32/(1.89[/tex] × [tex]10^4[/tex])

[tex]= 989.16s[/tex]

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