Ou have been called to testify as an expert witness in a trial involving a head-on collision. Car A weighs 1515 lb and was traveling eastward. Car B weighs 1125 lb and was traveling westward at 44.0 mph. The cars locked bumpers and slid eastward with their wheels locked for 17.5 ft before stopping. You have measured the coefficient of kinetic friction between the tires and the pavement to be 0.750 . How fast (in miles per hour) was car A traveling just before the collision

67.22 m/s

Explanation:

First, find deceleration which is equivalent to, where is coefficient of kinetic friction and g is acceleration due to gravity. Taking g as 32.2 then a=0.75*32.2=24.15 ft/s2

From kinematics

where v is final velocity and u is initial velocity. In this case, initial velocity is the common velocity and the final velocity is zero since they come to rest. S is the distance moved and a is deceleration. Substituting v with 0 and making u the subject then and by substitution

Converting ft per s to miles per hour, we multiply the above by 0.681818 hence u=29.073*0.681818=19.8225 mph

From the law of conservation of linear momentum, p=mv where m is mass and v is velocity, the sum of initial and final momentum are equal. In this case

By substitution considering the u is already known as 19.8225 mph

report

explanation:

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.