Why is it important to use standardized safety symbols on all hazardous products

Which sentence about particles in matter is true? a. atoms are present in solids and liquids but not in gases. b. the particles of matter are in constant motion. c. the same kinds of atoms are found in different elements. d. when a solid changes to a liquid, the sizes of the particles change.

Why does earth rotate? because earth is formed from cold gases collapsing due to gravity because the matter in the nebula that formed earth was spinning because earth forms more than 99% of the mass of the solar system because the hydrogen atoms inside the nebula fused to form helium

Athe top of a hill, an athlete on a skateboard has x joules of mechanical energy. how much mechanical energy will she have at the bottom of the hill? ignore the effects of friction.