Questions On Archimedes Principle 235cg

Questions on Archimedes principle In all the following questions use g = 9.82 ρair = 1.28kg/m3 and ρwater = 1000kg/m3 278. The weight of a metal cylinder was measured using a dynamometer in four different situations. The cylinder was located in: a) Air b) Partly submerged in water. c) Fully submerged in water. d) Fully submerged in saline water. The different experiments gave the following reading on the dynamometer. 1) 14.7N 2) 5.9N 3) 6.1N 4) 10.4N Decide which experiment that gave the different readings. 279. A hot air balloon has a mass of 300kg including the basket. The hot air inside the balloon weighs 17 000N. Determine the maximum load that the balloon is able to lift if it displaces 25 000N of cold air. 280. A barge floats inside a water filled dock. The barge is loaded with scrapiron. What would happen to the water filled dock, if suddenly all scrapiron was thrown overboard, ending up at the bottom of the dock? 281. A lock is always filled to the same level, regardless if it’s a large boat that enters the lock or if it is a small one. Does this mean that the pressure on the lock gate is different depending on the size of the boat that is inside the lock? 282. A stone has a density of 2.40g/cm3 and a volume of 18dm3 . Determine: • The mass of the stone. • The weight of the stone. • The apparent weight of the stone in air. • The apparent weight of the stone in water. 283. A couple of ice cubes floats in a glass of water. Will the water level in the glass change when the ice cubes has melted? Practical assignment Place a tub of water on the kitchen sink so that it balances on the edge of the washing-up sink. What will happen when letting a cup sail over the part of the tub that’s located over the washing-up sink. 1 Answers 278. A:1 B:4 C:3 D:2 279. It can carry a load of up to 5kN. Archimedes principle tells us that the buoyant force is 25kN − 17kN = 8kN The weight of the basket is 3kN 280. The water level decreases When the scrap-iron is inside the barge, a volume of water corresponding to the weight of the barge and the scrap-iron is displaced, this volume is larger than the volume of the scrap-iron since the

density of iron is larger than the density of water. 281. No, the pressure on the lock gate is always the same, since it only depends on the water level inside the lock. 282. • The mass of the stone is 43kg. m = ρstoneV • The weight of the stone is. Wstone = mg • The apparent weight of the stone in air is 0.42kN. Wair = ρairV g Wair = 1.29 · 0.018 · 9.82 = 0.23N Wapparent = Wstone − Wair = 424N − 0.23N = 424N So the buoyancy due to the surrounding air is negligible. • The apparent weight of the stone in water is 0.25kN Wwater = ρV g = 1.00 · 103 · 0.0018 · 9.82 = 177N Wapparent = Wstone − Wwater = 424N − 177N = 247N 283. No the water level doesn’t change. According to Archimedes principle the ice cubes float by displacing a volume of water equivalent to their weight. This volume is just the same volume of water that is ”created” when the ice melts.