Sometimes when I listen to music, I feel the need to get up and dance. Sometimes the music is so good, I want a dance partner, and my cat, Gigi, is usually the only option. So, she and I will go bopping around the house. As you might imagine, Gigi is not the biggest fan of being bopped, and eventually decides to jump from my arms. Together we have about 150 kg of mass, and Gigi still has her 3.5 kg of mass. If my bopping speed is 0.5 m/s, and Gigi’s speed after pushing off from me is 2 m/s, what velocity do I have as I am thrown back by my cat (and her indifference to my bopping needs)?

the first american roller coaster was the mauch chunk switchback railway, built in the mountains of pennsylvania in the mid-1800s. the track, originally built to send coal to a railway, was reconfigured as a "scenic tour."

neither accurate nor precise.

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.