Agrocery cart with a mass of 20 kg is pushed at constant speed along an aisle by a force f = 12 n. the applied force acts at a 20° angle to the horizontal.

find the work done by each of the forces on the cart if the aisle is 18 m long.

Explanation:

Given

mass of cart m=20 kg

Force applied F=12 N at angle of with horizontal

Force can be resolved in two components i.e. and

is will act Perpendicular to the motion of cart and will help to move the cart .

Since cart is moving with constant velocity therefore net force is zero on the cart as friction is opposing the

Work done by is

Work done by Friction will be same but in Opposite Direction

Work done by  is

because direction of force and motion is Perpendicular to each other.              

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.