Provide two reasons why is bronze still used in the manufacture of bells?

According to social exchange theory, altruistic behaviors benefit the individual who performs them.

To do work, this truck uses energy stored in chemical fuel and an electrical battery. how much total energy does this truck put out?

The mass of the sun is 1.99×1030kg and its distance to the earth is 1.50×1011m. what is the gravitational force of the sun on the earth?