Ariella drove 40 miles to see her cousin. The trip took Ariella 2 hours. Then drove from her cousins house to a store for 30 miles. It took Ariella to hours to Ariella to arrive at the store. What was the average speed of the trip

Which of the following correctly describes what happens when an atomic bomb explodes? small pieces of fissionable material are joined and form a body with a mass greater than the critical mass, the relative number of neutrons escaping decreases, and a chain reaction and explosion result. large pieces of fissionable matter are brought together quickly and form a body with a mass smaller than the critical mass, the relative number of escaping neutrons increases, and a chain reaction and explosion result.