From 1962 until 1981 pennies were made from 95% copper and 5% zinc and had a mass of 3.1 g. Starting in 1982, pennies have been made from 97.5% zinc and 2.5% copper and have a mass of 2.5 g. Suppose you have a sample of pennies that consists of 43.6% pre-1982 pennies. Determine the average mass of a penny in this sample.

Two nitro no2 groups are chemically bonded to a patch of surface. they can't move to another location on the surface, but they can rotate (see sketch at right). it turns out that the amount of rotational kinetic energy each no2 group can have is required to be a multiple of ε, where =ε×1.010−24 j. in other words, each no2 group could have ε of rotational kinetic energy, or 2ε, or 3ε, and so forth — but it cannot have just any old amount of rotational kinetic energy. suppose the total rotational kinetic energy in this system is initially known to be 32ε. then, some heat is removed from the system, and the total rotational kinetic energy falls to 18ε. calculate the change in entropy. round your answer to 3 significant digits, and be sure it has the correct unit symbol.

Transportation is the largest single source of air pollution in the united states. air pollution can harm the environment and human health. which technology could offer a solution to this problem? mufflers that reduce noise motors that run on electricity tires that improve gas mileage

Pls ill give u brainliest which of the following is true about science? 1. political conditions are unable to influence it. 2. economic concerns may prevent it from solving problems.