1. You need to have 6,000 Joules of kinetic energy to knock down a building with a wrecking ball. Use the
graphs to determine the combinations of mass and speed that will give you 6,000 joules of energy.

Which best describes the present-day universe? opaque, expanding very slowly, stars produce heavy elements transparent, expanding at an accelerated rate, stars produce heavy elements opaque, expanding at an accelerated rate, stars produce only hydrogen and helium transparent, expanding very slowly, stars produce only hydrogen and helium