What does an astronomer mean by "the universe"

Which type of current is produced by a wire breaking magnetic field lines and changing the polarity? a. alternating b. direct c. straight d. alternating and direct

Two objects of different mass start from rest, are pulled by the same magnitude net force, and are moved through the same distance. the work done on object 1 is 900 j. after the force has pulled each object, object 1 moves twice as fast as object 2. how much work is done on object 2?

Argon, neon, and xenon are examples of