A15-ft ladder rests against a vertical wall. if the top of the ladder slides down the wall at a rate of 0.33 ft/sec, how fast, in ft/sec, is the bottom of the ladder sliding away from the wall, at the instant when the bottom of the ladder is 9 ft from the wall? answer with 2 decimal places. type your answer in the space below. if your answer is a number less than 1, place a leading "0" before the decimal point (ex: 0.35).

Let the corner of the wall and floor is our origin

Now the end of the ladder is on the floor is at distance x and top end on the wall is at distance y from this corner.

So we will use Pythagoras Theorem to find the length of the ladder.

now if we differentiate whole equation with time

now the speed of the end of the ladder at the end of the floor will be given as

here is the speed of end of the ladder on the wall.

so here we also know that

now we will plug in all values in the equation

so the end of the ladder on the floor will move with speed v = 0.44 ft/s

probably not if net force is zero

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.