17. A skateboard has a mass of 3.2 kg. If it slips out from a skateboarder and has
a velocity of 1.0 m/sex, what is the momentum of the skateboard?

18. You drop your physics textbook on your big toe. If the textbook has a mass of
m) = 2.18 kg. The book is in freefall, calculate the force when the book hits
your foot.

19. Suppose that you lift your foot and kind of catch the book. I say kind of catch
the book because as the book hits your foot, you slowly lower it to the
ground. Will your big toe hurt more or less than it did problem 18?

20. What was the change in momentum from problem 19 if it took half a second
for the book to come to rest?

Explanation:

The momentum of any object  = m v

here m is the mass of body and v is its velocity

Thus momentum P = 3.2 x 1 = 3.2 kg-m

As the book is falling freely , so it will fall with and acceleration g

The force exerted by it is = m g

Thus force = 2.18 x 10 = 21.8 N

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.

because if the tool that you are using is not balanced it there would be false mass.