Questions

The Doppler effect or Doppler shift is the change in frequency or wavelength of a wave in relation to an observer who is moving relative to the wave source. 

Oxytocin is a mamallian hormone and also acts as neuro transmitter in the brain.

Dust particles such as coal dust(smoke) are fine particle of a solid (carbon in the case of smoke) dispersed in air. They are colloidal systems and the particles are charged either positive or negative. In an applied electrical field, they are attracted towards the opposite electrodes. Movement of the particles towards the electrodes is known as 'electrophoresis'. Hence electrophoresis is applied to remove smoke within the chimeny itself without allowing it to escape into the air and cause nuisance.

The color of giraffe's tongue is purple or bluish to prevent it from sunburn as it lives in tropical regions.

Let amount of milk removed = 2x litre
So, amount of water added = x litre
Now → (165 − 2x)/x = 5/3
x = 45 lit