Which set of procedures and observations indicates a chemical change?
(1) ethanol is added to an empty beaker and the ethanol eventually disappears.
(2) a solid is gently heated in a crucible and the solid slowly turns to liquid.
(3) large crystals are crushed with a mortar and pestle and become powder.
(4) a cool, shiny metal is added to water in a beaker and rapid bubbling occurs.

question: ray weighs 100 kilograms, his wrestling partner, bobby, weighs 50 kilograms. if ray moves at 4 m s , how fast will bobby have to run at him to apply an equal amount of kinetic energy?

answer: 8 m/s he needs to run twice as fast to keep up so he has some work to do

explanation:   if the mass has units of kilograms and the velocity of meters per second, the kinetic energy has units of kilograms-meters squared per second squared.

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(jacemorris04)