Mechanical Equivalent of Heat

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Mechanical Equivalent of Heat II. OBJECTIVE: The main purpose of this lab is to understand how work is transformed into heat. And also to understand the relationship between this two, which is mechanical energy. In order to calculate this we going to have to find the values of work and heat. III. THEORY AND METHOD OF INVESTIGATION: The mechanical equivalent of heat is the relationship between units of heat energy and units of mechanical energy. Heat energy has traditionally been measured in units of calories and likewise mechanical energy is measured in Joules. However, since heat is a form of energy, it also could be measured in Joules. The SI unit for energy has been designated as Joules. The unit of calorie is defined at the heat energy needed to raise 1 gram of water one degree Celsius. Therefore, the heat capacity of water is C = l calorie/g/°C. In general, the heat absorbed by a body is given by Q = m C ΔT (1) Where Q is the heat gained in calories, m is the mass, ΔT is the temperature change, and C is the heat capacity of the body. In this experiment, frictional forces heat an aluminum calorimeter. The work of friction should be equal to the heat energy gained by the calorimeter. The heat energy gain can be easily found by measuring the change in temperature (ΔT) and by knowing the mass of the aluminum calorimeter (Mc). The heat energy gain Q is given by Equation (2). Q = Mc Cc ΔT (2) Where Cc = 0.215 cal/(g °C) A nylon cord is wound five times around the aluminum calorimeter. The frictional force between the band and the calorimeter is large enough that one end of the band can lift a 10 kg weight while the other end becomes slack. As a result of this mechanical trick, the frictional force is equal to the weight of the 10 kg mass and is to a large extent independent of the speed at which the drum is rotated. The work of friction (Wf) is

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