Dylan is trying to lift his bike into the back of his pick-up truck of height h. He attaches a light string to it and pulls it vertically upward. If the bike is the system, what kind of work do Dylan and Earth do on the bike?

Scientists follow specific processes in order to determine valid explanations and conclusions from observations. david observed strange lights in the sky above his home outside of roswell, new mexico. the only explanation that makes sense to him is that there are ufos in the area. what should david do next to verify his explanation?