17.2 - MasteringPhysics 11/19/08 6:12 PM Assignment Display...

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11/19/08 6:12 PM MasteringPhysics Page 1 of 14 http://session.masteringphysics.com/myct Assignment Display Mode: View Printable Answers Physics 5D Fall 2008 Assignment 4 Due at 11:59am on Wednesday, November 5, 2008 View Grading Details USEFUL ADVICE FOR PROBLEM SOLVING: In all these problems (and most thermodynamics problems) you have to use energy balance equations. Define your system, and its final and initial states. Consider what happens to its energy during that transformation (does it receive heat or does it lose heat?), and where does this energy come from? For example in a typical problem, for an isolated system A+B which are put in contact, we say after equilibrium is reached some heat has gone from A to B. Usually by equating the heat lost from A to that gained by B, we can find our answer. Heat can also come from other types of energy (electrical or mechanical). So writing all these energy transformations will lead you to the answer. We will see more of that next in the statement of first law. .. Problem 19.26 Description: A m ice-skater moving at v glides to a stop. (a) Assuming the ice is at 0 degree(s) C and that 50 % of the heat generated by friction is absorbed by the ice, how much ice melts? A 56 ice-skater moving at 8.5 glides to a stop. Part A Assuming the ice is at 0 and that 50 of the heat generated by friction is absorbed by the ice, how much ice melts? Express your answer using two significant figures. ANSWER: = Specific Heat, Latent Heat, and Temperature versus Time Graphs Description: An introduction to specific heat and latent heat, with an emphasis on interpreting temperature versus time graphs under constant heating/cooling conditions. Learning Goal: To understand specific heat and latent heat and how they are related to temperature versus time graphs. Energy can be added to a system either by doing work on it or by adding heat to it. Energy transfer by work requires a force to act through some distance. Energy transfer in the form of heat occurs between objects that are at different temperatures, with energy spontaneously traveling from the higher-temperature object to the lower-temperature one. When energy is added to an isolated system in the form of heat, either the temperature of the system will increase or the system will undergo a phase change at a fixed temperature. The specific heat of a sample characterizes the rate at which it changes temperature per unit mass when it receives energy in the form of heat. The relationship between the energy input in the form of heat and the resulting temperature change is , where is the mass of the sample and is its specific heat, which depends on its phase. For this problem, assume that specific heat values are a constant for all temperatures within a given phase, which is a good approximation. The latent heat
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17.2 - MasteringPhysics 11/19/08 6:12 PM Assignment Display...

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