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 204- rad/s. One such flywheel is a solid, homogeneous cylinder with a mass of 450 kg and a radius of 1.0 m. What is the kinetic energy of the flywheel after charging?

If the truck operates with an average power requirement of 7.5kW, for how many minutes can it operate between chargings?

Explanation / Answer

Here ,

angular speed , wf = 204pi rad/s

mass , m = 450 Kg

radius , r = 1 m

kinetic energy of wheel =0.5 * I * w^2

kinetic energy of wheel = 0.5 * 0.5 * m * r^2 * w^2

kinetic energy of wheel = 0.5 * 0.5 * 450 * 1^2 * (204 * pi)^2

kinetic energy of wheel = 4.619 *10^7 J

the kinetic energy of wheel is 4.619 *10^7 J

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let the time between charging is t

as energy = power * time

4.619 *10^7 J = 7.5 *10^3 W * t

t = 6158.7 s = 102.6 minutes

the truck can operate for 102.6 minutes

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