Aflywheel 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 310-mile trip in a typical midsize car produces about 1.10 109 j of energy. how fast would a 12-kg flywheel with a radius of 0.32 m have to rotate to store this much energy? give your answer in rev/min.

Explanation:

Given:

energy to be stored in a flywheel,

mass of the flywheel,

radius of the flywheel,

To find:

rotational speed, N=?

We know that kinetic energy of a flywheel can be given by:

.................................(1)

&

......................................(2)

where:

I=moment of inertia

= angular velocity in radian per second

putting respective values in eq. (2)

Now, from eq. (1)

∵    

scattering of light by tiny particles in air to produce the colors we see on sky, is dependent on the following factors:

(i) wavelength of light

(ii) size of the scattering particle  

(iii) distance traveled by light through the atmosphere.

according to rayleigh's law of scattering, the amount of scattering is inversely proportional to the fourth power of its wavelength. shorter the wavelength, greater is its scattering. hence violet/blue light is scattered more than red.

sun's light is a composite light ( visible light) with wavelengths in the range 400 nm (violet) to 700 nm (red). as sunlight passes through our atmosphere, the molecules of air scatter light according to their wavelengths. during sunrise and sunset, the sun's position is below the horizon. hence light from the sun travels a greater distance in the atmosphere when compared to its position a noon.

as sunlight enters the earth's atmosphere, blue light is scattered away and at the end of its journey in the sky, only red and orange wavelengths remain in the beam.

hence at sunrise and sunset, the sky appears reddish orange.

b. false

explanation:

suppose a rock in free fall is dropped off a cliff. after falling for 5 seconds, its speed would not be 100 m/s.