CHECK QUESTIONS: Which has the greater density, a cupful of water or a lake full of water? A kilogram of lead or a kilogram of feathers? A single uranium atom or the world? TABLE 12.1 Densities of Common Substances (kg/m) (For density in g/cm, divide by 1000) Solids Density Iridium 22,650 Osmium 22,610 Platinum 21,090 Gold 19,300 Uranium 19,050 Lead 11,340 Silver 10,490 Copper 8,920 Brass 8,600 Iron 7,874 Tin 7,310 Aluminum 2,700 Concrete 2,300 Ice 919 Liquids Mercury 13,600 Glycerin 1,260 Seawater 1,025 Water at 1,000 Ethyl alcohol 785 Gasoline 680 2009 Pearson Education, Inc. CHECK QUESTIONS Which has more surface area, an elephant or a mouse? 2000 kilograms of elephant or 2000 kilograms of mice? CH 12-1 CONCEPTUAL Physics- NEXT-TIME QUESTION Material Strength B C. If you drill a hole horizontally through the branch of a tree, you risk weakening the branch. For minimum weakening, drill the hole through the a) upper part, A. b) middle part, B. c) lower part, C. d) makes no difference. Howit NEXT-TIXE QUESTION WHY IS WET SAND FIRMER BENEATH YOUR FEET THAN WET GRAVEL? -CONCEPTUAL Physics NEXT-TUXE QUESTION ?N 100N CONSIDER AN INFANT WHO WEIGHS 100 NEWTONS. DURING A YEAR SHE GROWS SO THAT EACH DIMENSION OF HER BODY INCREASES BY 5%. HOW MUCH WILL SHE THEN WEIGH? (ASSUME HER DENSITY REMAINS UNCHANGED.) CONCEPTUAL Physics NEXT-TIXE QUESTION COMPARED TO AN EMPTY SHIP. WILL A SHIP LOADED WITH A CARGO OF STYROFOAM FLOAT LOWER IN WATER OR HIGHER IN WATER? CONCEPTUAL Physics- NEXT-TIME QUESTION EVERYBODY KNOWS THAT "WATER SEEKS ITS OWN LEVEL," BUT VERY FEW PEOPLE KNOW WHY WATER SEEKS ITS OWN LEVEL. THE REASON HAS MOST TO DO WITH 27 a) ATMOSPHERIC PRESSURE. b) WATER PRESSURE DEPENDING ON DEPTH. c) WATER'S DENSITY. CONCEPTUAL Physics- NEXT-TIXE QUESTION A FIRE TRUCK CARRYING A LOAD OF FIRE FIGHTERS AND A LARGE TANK OF WATER IS ABOUT TO CROSS A BRIDGE THAT MAY NOT SUPPORT THE LOAD. THE CHIEF SUGGESTS THAT SOME OF THE PEOPLE ABOARD GET INTO THE TANK SO THE LOAD WILL BE LESS. IS THIS A GOOD IDEA OR A POOR IDEA? EXPLAIN.