What can experiments tell us that other studies cant

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 •  

Match each type of lever with the correct diagram. 1. first-class 2. third-class 3. second-class

Which statements identify what astronomers currently know and think will happen with our universe? check all that apply. the big bang produced dark energy, which accounts for some of the energy needed to expand the universe. the vastness of space may contain a type of matter known as "dark matter." the universe is currently shrinking at a rapid rate. the universe is currently expanding at an accelerating rate. the big bang theory explains all the energy and matter discovered by scientists.