A helicopter is flying at a height of 1.5km. If it has 50MJ of G. P.E., what is the mass of the helicopter?

What is the role of lenses in microscopy?

Two models of the same compound are shown. in what way is model b better than model a? model b shows the types of elements in the compound, but model a does not. model b shows the three-dimensional shape of the molecule, but model a does not. model b shows how the atoms in the molecule are connected, but model a does not. model b shows the number of atoms of each element in the molecule, but model a does not

Why did thomson's results from experimenting with cathode rays cause a big change in specific thought about atoms ?