A 39.1 kg woman wearing ice skates is standing on a skating rink next to a vertical wall. She pushes off against the wall and begins to slide along the perfectly horizontal surface of the rink. The coefficient of kinetic friction between the blades of her ice skates and the surface of the rink is 0.04. If she slides a distance of 14.8 m before stopping and her push against the wall lasted 0.2 s, what was the average force (in N) that she exerted on the wall?

666.67N

Explanation:

from work energy principle

work done by friction = change in KE

-uk*m*g*x = (1/2)*m*(vf^2-vi^2)

-uk*g*x = (1/2)*(vf^2-vi^2)

as the woman is stopped the final velocity vf = 0

-0.04*9.8*14.8 = (1/2)*(0-vi^2)

initial speed vi = 3.41 m/s

after pushing against the wall

momentum gained by woman = m*vi

force applied F = m*vi/t

F = 39.1*3.41/0.2

F = 666.66 N <<

explanation:

could i give you a exaplo that could you?

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.