Delivery trucks that operate by making use of energy stored in a rotating flywhe

Question

Delivery trucks that operate by making use of energy stored in a rotating flywheel have been used in Europe. The trucks are charged by using an electric motor to get the flywheel up to its top speed of 186- rad/s. One such flywheel is a solid, homogeneous cylinder with a mass of 460 kg and a radius of 1.0 m. What is the kinetic energy of the flywheel after charging?

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If the truck operates with an average power requirement of 7.0kW, for how many minutes can it operate between chargings?

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Explanation / Answer

KE=(1/2)*I*w^2

w=186- rad/s.

I=?

I=.5mr^2

=.5(460)(1.0)^2

=230
What is the kinetic energy of the flywheel after charging

Now plug that into the equation for KE

KE=.5(230)(186*pi)^2

=3.9266x10^7 J

If the truck operates with an average power requirement of 7.0kW, for how many minutes can it operate between chargings

Since 1 J = 1 kg·m^2/s^2

and 1W = 1 kg·m^2/s^3,

=3.9266*10^7/7000 = 5609.42

= 5609.42 / 60

=93.49 min.

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