My notes a student throws a heavy red ball horizontally from a balcony of a tall building with an initial speed v0. at the same time, a second student drops a lighter blue ball from the same balcony. neglecting air resistance, which statement is true?

a. the blue ball reaches the ground first.
b. the balls reach the ground at the same instant.
c. the red ball reaches the ground first.
d. both balls hit the ground with the same speed. none of the above statements are true.

B. The balls reach the ground at the same instant.

Explanation:

M = Mass of Earth = 5.972×10²⁴ kg

r = Radius of Earth = 6.371×10⁶ m

G = Gravitational constant = 6.67 × 10⁻¹¹ m³/kgs²

t = Time taken

u = Initial velocity

v = Final velocity

s = Displacement

a = Acceleration

From the equation above it can be seen that all objects irrespective of mass falls at the same acceleration.

If both bodies are initially at rest and travel the same distance the time the bodies will take to reach the ground will be same.

the small 0.38-kg slider is known to move from position a to position b along the vertical-plane slot. determine (a) the work done on the body by its weight and (b) the work done on the body by the spring. the distance r = 0.70 m, the spring modulus k = 154 n/m, and the unstretched length of the spring is 0.53 m

explanation:

-reverse card

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.