Select an example of a vertical motion with a positive velocity and a negative acceleration. select the correct example and explanation. a)a tossed ball on its way down. as the ball moves down it is slowing down, hence the acceleration is opposite the bvelocity (negative).b) a tossed ball on its way upward. as the ball moves upward it is slowing down, hence the acceleration is pointing in the same direction as the velocity (negative).c) a tossed ball on its way upward. as the ball moves upward it is slowing down, hence the acceleration is opposite the velocity (negative).d) a tossed ball on its way down. as the ball moves down it is slowing down, hence the acceleration is pointing in the same direction as the velocity (negative).

c)

Explanation:

When a ball is tossed upward, it rises due to the initial velocity which points upward (so it is positive if we choose the upward direction as positive), but once released, the only force (neglecting air resistance) acting on the ball is gravity.

This force is due to the mass of the Earth, and produces an acceleration in the same direction than the force, which is always downward, so in this case is negative.

As it has opposite direction to the velocity, causes the ball to slow down until it reach to a point when momentarily comes to an stop, and then changes direction falling with negative velocity, so it speeds up as it has the same sign than acceleration, that it is always present.

it would be kevlar ^^

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.