ch13_14_solns - 10. (II) To make a secure fit, rivets that...

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10. (II) To make a secure fit, rivets that are larger than the rivet hole are often used and the rivet is cooled (usually in dry ice) before it is placed in the hole. A steel rivet 1.871 cm in diameter is to be placed in a hole 1.869 cm in diameter at 20°C. To what temperature must the rivet be cooled if it is to fit in the hole? 10. The rivet must be cooled so that its diameter becomes the same as the diameter of the hole. ( 29 ( 29 ( 29 0 0 0 0 o o 0 0 6 o 0 1.869 cm 1.871 cm 20 C 69 C 12 10 C 1.871 cm L L T L L L T T L L T T L α - ∆ = - = - - - = + = + = - 37. (II) A hot-air balloon achieves its buoyant lift by heating the air inside the balloon, which makes it less dense than the air outside. Suppose the volume of a balloon is 3 m 1800 and the required lift is 2700 N (rough estimate of the weight of the equipment and passenger). Calculate the temperature of the air inside the balloon which will produce the required lift. Assume that the outside air temperature is 0°C and that air is an ideal gas under these conditions. What factors limit the maximum altitude attainable by this method for a given load? (Neglect variables like wind.) 37. There are three forces to consider: the buoyant force upwards (which is the weight of the cold air displaced by the volume of the balloon), the downward weight of the hot air in the
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ch13_14_solns - 10. (II) To make a secure fit, rivets that...

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