Why is the hr diagram important to scientists?

the hr diagram shows the composition of stars.
the hr diagram shows the shape of stars.
the hr diagram groups the stars by their sizes.
the hr diagram groups stars by their position in the sky.

Gasoline comes from petroleum, which is made from ancient living things. petroleum, therefore, contains a type of energy. a. heat b. nuclear c. biological d. chemical potential

Cathy is pedaling down a steep hill on her bicycle and wants to be able to coast up the next hill, which is 25 meters high, without pedaling. cathy and her bicycle have a mass of 75 kg. assuming her bicycle is 100% efficient, what would her speed have to be?

Which pair of quantities includes one quantity that increases as the other decreases during simple harmonic motion?