Answer:
detecting and indicating an electric current
Answer:
second one is correct that is right
This phenomena is also called the Doppler shift. When the source of light is approaching towards an observer, the color tends to be blue shifted, but when the source is moving away or being stretch, the color tends to red shifted. In astronomy it can be use how fast galaxy is moving towards us or how fast it moves away.
maximum speed of cheetah is

speed of gazelle is given as

Now the relative speed of Cheetah with respect to Gazelle


now the relative distance between Cheetah and Gazelle is given initially as "d"
now the time taken by Cheetah to catch the Gazelle is given as

so by rearranging the terms we can say


so above is the relation between all given variable