Question

A car is designed to get its energy from a rotating flywheel in the shape of a uniform, solid disk of radius 0.550 m and mass 560 kg. Before a trip, the flywheel is attached to an electric motor, which brings the flywheel's rotational speed up to 5.10 ✕ 103 rev/min.

a)Find the kinetic energy stored in the flywheel (in J).

b)If the flywheel is to supply energy to the car as a 12.0 hp motor would, find the length of time in hours the car could run before the flywheel would have to be brought back up to speed.

Answer #1

First we calculate the kinetic energy of the flywheel by moment of inertia and rotational speed.

Then we find the time for which the flywheel be able to provide energy to the motor.

A car is fitted with an energy-conserving flywheel, which in
operation is geared to the driveshaft so that the flywheel rotates
at 240 rev/s when the car is traveling at 80 km/h. The total mass
of the car is 950 kg; the flywheel weighs 200 N and is a uniform
disk 1.1 m in diameter. The car descends a 1300-m-long, 5° slope,
starting from rest, with the flywheel engaged and no power
generated from the engine. Neglecting friction and the...

A futuristic design for a car is to have a large solid
disk-shaped flywheel within the car storing kinetic energy. The
uniform flywheel has mass 370 kg with a radius of 0.500 m and can
rotate up to 140 rev/s. Assuming all of this stored kinetic energy
could be transferred to the linear velocity of the 1600-kg car,
find the maximum attainable speed of the car.

Consider a bus designed to obtain its motive power from a large
rotating flywheel (i.e. solid disk) that has a mass of 1400kg and
diameter of 1.5m. The flywheel is periodically “recharged” to its
maximum speed of 3600 rpm by an electric motor at the bus terminal.
If the bus requires an average power of 12 kW, how long will it
operate between recharges? For reference, the moment of inertia of
a solid disk is I =(mr^2 )/2.

Trucks can be run on energy stored in a rotating flywheel, with
an electric motor getting the flywheel up to its top speed of 611
rad/s. One such flywheel is a solid, uniform cylinder with a mass
of 551 kg and a radius of 1.1 m that rotates about its central
axis. What is the kinetic energy of the flywheel after
charging?
If the truck uses an average power of 6.5 kW, for how many
minutes can it operate between...

From this week's lab you learned that the change in
gravitational potential energy of a falling body can be captured
and stored as a rotational kinetic energy of a spinning disk. This
gave you the idea of a regenerative driver for an elevator in a
tall building. When an elevator goes down the corresponding change
in the gravitational potential energy of the elevator is
transformed into the rotational kinetic energy of a solid
disk-shape flywheel which can be extracted and...

Assessment
Identify the Variables!
In rotational kinematics - the variables are:
t = time, which is measured in s (for seconds)
θ = angle = what angle did the object turn thru, usually
measured radians
ωO = initial angular velocity = the rotational speed
of the object at the beginning of the problem, which is measured in
rad/s
ω = final angular velocity = the rotational speed of the object
at the end of the problem, which is measured in...

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