A70-n block rests on a 30° inclined plane. a. determine the normal force. b. determine the friction force that keeps the block from sliding. c. what push directed up the plane will cause the block to move up the plane with constant speed if the force of friction is 18 n? draw a neat, labeled free body diagram.

Given that:

W = weight of the block = mg = 70 N

mass of the block is given as

m = W/g

m = 70/9.8 = 7.14 kg

a)

N = normal force on the block

Perpendicular to incline , force equation is given as

N = m g cos30

inserting the values

N = (70) Cos30

N = 60.6 N

b)

f = frictional force acting on the block to keep it from sliding

Parallel to incline force equation is given as

f = m g Sin30

f = (70) Sin30

f = 35 N

c)

F = pushing force

f = frictional force = 18 N

Parallel to incline force equation is given as

F = f + mg Sin30

F = 18 + (70) Sin30

F = 53 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.