Flywheel Kinetic Energy in Delivery Trucks

[BuBbLeS01]

Homework Statement

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 960 rad/s. One such flywheel is a solid homogenous cylinder, rotating about its central axis, with a mass of 550 kg and a radius of 0.65 m. What is the kinetic energy of the flywheel after charging?

If the truck operates with an average power requirement of 9.3 kW, for how many minutes can it operate between charging?

Homework Equations

K = 1/2Iw^2
I = 1/2mr^2

The Attempt at a Solution

K = 1/2 * (.5 * 550 * .65^2) * 960^2 = 5.35 x 10^7
I a, getting a really huge number I wanted to make sure I am doing it right.

 

[JFonseka]

Well convert radians per second to metres per second.

Then K = 0.5 (m) (v)^2

 

[ogb p]

Your calculations for the kinetic energy of the flywheel after charging are correct. The large number is expected as the flywheel has a high rotational speed and a significant mass. This stored energy can then be used to power the delivery truck.

To calculate the operational time of the truck, we can use the equation P = E/t, where P is the power requirement, E is the energy stored in the flywheel, and t is the operational time. Rearranging the equation, we get t = E/P.

Plugging in the values, we get t = (5.35 x 10^7 J) / (9.3 x 10^3 W) = 5753 seconds or approximately 1.6 hours. This means that the truck can operate for 1.6 hours between charging, assuming it maintains an average power requirement of 9.3 kW.