A0.50 kilogram ball is held at a height of 20 meters. what is the kinetic energy of the ball when it reaches halfway after being released? a. 49 joules b. 98 joules c. 1.0 × 10^2 joules d. 1.1 × 10^2 joules

A. 49 joules

Step By Step Solution:

Via kinematic equations we can must first determine the velocity of this object after 10 meters (since halfway of 20 meters is 10).

Where the initial velocity is zero since it's held at a height of 20 meters, hence it's not moving initially, g is the average gravity on Earth 9.8 m/s^2 and d is the distance this object will travel so 10 meters. By plugging these values in we obtain:

And the equation for kinetic energy is :

So the kinetic energy halfway after being released is 49 joules.

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.

it is a negative acceleration