Physics
posted by StressedStudent .
A flywheel is a solid disk that rotates about an axis that is perpendicular to the disk at its center. Rotating flywheels provide a means for storing energy in the form of rotational kinetic energy and are being considered as a possible alternative to batteries in electric cars. The gasoline burned in a 482mile trip in a typical midsize car produces about 3.38 x 109 J of energy. How fast would a 26.0kg flywheel with a radius of 0.222 m have to rotate to store this much energy?

(1/2) I w^2 = 3.38*10^9
I = (1/2) m r^2 = (1/2)(26)(.222)^2
= .641 kg m^2
(1/2) I = .320 kg m^2
so
.320 w^2 = 3.38 * 10^9
w^2 = 10.55 *10^9 = 1.055 * 10^10
w = 1.03 * 10^5 radians/s
= .163 * 10^5 revolutions/sec
= 9.81 * 10^5 rpm
981,000 rpm
forget about it. If the axis were level, you could not turn it without flipping over but no matter how strong the material it would have flown apart by then. 
I suppose you could have contra rotating flywheels pointed at each other to prevent the gyroscopic flip over problem, but you still can not get that sort of rpm practically even in a vacuum with magnetic suspension bearings without the material flying apart from centripetal acceleration stress. Something has o hold the material at the outside in toward the center and that is the radial tensile stress in the material.

Set the rotational kinetic energy equal to 3.39*10^9 Joules, and solve for the angular velocity, w.
The rotational KE is (1/2)*I*w^2
The moment of inertia of a solid disc about the center is
I = (1/2)MR^2 
By the way, we tried this.
Respond to this Question
Similar Questions

physics.
A flywheel is a solid disk that rotates about an axis that is perpendicular to the disk at its center. Rotating flywheels provide a means for storing energy in the form of rotational kinetic energy and are being considered as a possible … 
Physics
The moment of inertia of an object depends on the shape of the object, location and orientation of the axis of rotation. For a solid disk, when the disk is rotating about an axis that is perpendicular to the disk and passing through … 
physics
hi,need help please.thank. A car is designed to get its energy from a rotating flywheel (solid disk) with a radius of 2.00 m and a mass of 525 kg. Before a trip, the flywheel is attached to an electric motor, which brings the flywheel's … 
phys
A disk rolls down a slope. It rotational axis is its center of mass. It is rotation at a constant angular speed making 34.0 full revolutions in a time interval of 3.30 s. 1)What is the rotational inertia of the disk if its mass is … 
physics
An experimental flywheel, used to store energy and replace an automobile engine, is a solid disk of mass 202.0 kg and radius 0.35 m. (a) What is its rotational inertia? 
physics
A car is designed to get its energy from a rotating flywheel (solid disk) with a radius of 1.00 m and a mass of 600 kg. Before a trip, the flywheel is attached to an electric motor, which brings the flywheel's rotational speed up to … 
physics
A car is designed to get its energy from a rotating flywheel (solid disk) with a radius of 1.00 m and a mass of 600 kg. Before a trip, the flywheel is attached to an electric motor, which brings the flywheel's rotational speed up to … 
pysics
Consider a 6·kg disk with a radius of 0.6·m and rotating about an axis passing through its center. (a) What is its rotational inertia? 
physics
A disk with a rotational inertia of 1.4 kg×m2 and a radius of 0.8 m rotates on a frictionless fixed axis perpendicular to the disk faces and through its center. A force of 5.2 N is applied tangentially to the rim. The angular acceleration … 
physics
A flywheel is a solid disk that rotates about an axis that is perpendicular to the disk at its center. Rotating flywheels provide a means for storing energy in the form of rotational kinetic energy and are being considered as a possible …