140 students sit in an auditorium listening to a physics lecture. because they are thinking hard, each is using 125 w of metabolic power, slightly more than they would use at rest. an air conditioner with a cop of 5.0 is being used to keep the room at a constant temperature. what minimum electric power must be used to operate the air conditioner?

P = 3500 W

Explanation:

Given :

Total number of students in the auditorium is n = 140

Metabolic power each student is using is p = 125 W

The coefficient of performance ( COP ) of the air conditioner is given as 5 to maintain a constant temperature inside the auditorium.

Let the minimum electric power that must b used to run the air conditioner be P.

We know that

COP = np / P

P = np / COP

 = ( 140 x 125 ) / 5

 = 3500 W

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.

air exerts forces on falling objects near earth’s surface.

explanation:

the term 'free falls' refer to object that are falling towards the earth, in a situation in which gravity is the only force acting on the object.

for an object in free fall, the acceleration is constant (g, the gravitational acceleration), and so the velocity of the object constantly increases.

for objects near earth's surface, there is always another force acting on the object: the resistance due to the air. this force is opposed to the direction of fall of the object, and it is proportional to the velocity of the object, so as the object falls down, this force increases up to a point when it balances the force of gravity, and the object continues its motion at constant velocity (called terminal velocity). since in this case gravity is not the only force acting on the object, we are not in a situation of free fall.