Abus is designed to draw its power from a rotating flywheel that is brought up to 3000 rpm by an electric motor. the flywheel is a solid cylinder of mass 2000 kg and diameter 1 m. if the bus requires an average power of 20 kilowatts, how long will the flywheel rotate?

620 s

830 s

980 s

1,200 s

2,500 s

To solve this problem we will apply the concept of rotational kinetic energy. Once this energy is found we will proceed to find the time from the definition of the power, which indicates the change of energy over time. Let's start with the kinetic energy of the rotating flywheel is

Here

I = moment of inertia

Angular velocity

Here we have that,

Replacing the value of the moment of inertia for this object we have,

The expression for average power is

Therefore the correct answer is 620s.

answer;

d. are made mostly of liquid

explanation;

-the general   composition and structure planets includes; they have a thick gas and liquid layer covering a small,solid core. mostly the gases are hydrogen and helium atmosphere and layers of liquid hydrogen. for instance neptune and uranus are examples of the outer planets, they have a core covered by ice and ammonia.

-neptune's atmosphere is hydrogen and helium with a bit of methane so there is no oxygen to breath and the interior is made up of frozen water and ammonia with a rock and iron core. thus, there is no liquid water or solid surface to survive.