Which of the following is an explanation of the charging foul?

Consider a system to be two train cars traveling toward each other. what is the total momentum of the system before the train cars collide?   kg • what must the total momentum of the system be after the train cars collide?   kg •  

Which statement best describes the superposition principle? a.) if two in-phase waves arrive simultaneously at a point, their amplitudes add up b.) if two out-of-phase waves arrive simultaneously at a point, their amplitudes add up c.) if two in-phase waves arrive at a point one after another, their amplitudes add up d.) if two out-of-phase waves arrive at a point one after another, their amplitudes adds up

1. when conducting a test on what kind of music increases the growth of plants, all of the following would fail to meet to fair test standard except (1 point) using different kinds of plants. giving some plants more water than others. exposing the plants to different types of music. using nutrient-rich soil for one and lesser soil for others. 2. engineering uses scientific thinking to solve real-world problems. (1 point) true false 3. what does it mean to test a hypothesis? (1 point) pass a quiz on other scientists’ results analyze only the results from scientific sources not make assumptions about how an experiment will turn out see if the results of an experiment are what the scientist predicted