![]() A baseball player throwing a ball, for example, increases both the ball’s kinetic and potential energy. Forces exerted by the body are non-conservative, so that they can change the mechanical energy \((KE + PE)\) of the system worked upon, and this is often the goal. Useful work does include that done in climbing stairs or accelerating to a full run, because these are accomplished by exerting forces on the outside world. It's one of the four laws of thermodynamics, which describe the. Useful work requires a force exerted through a distance on the outside world, and so it excludes internal work, such as that done by the heart when pumping blood. The second law of thermodynamics states that as energy is transferred or transformed, more and more of it is wasted. Work done by a person is sometimes called useful work, which is work done on the outside world, such as lifting weights. Table shows energy and oxygen consumption rates (power expended) for a variety of activities. (See Figure7.09.1.) Approximately 20 kJ of energy are produced for each liter of oxygen consumed, independent of the type of food. We can measure the energy people use during various activities by measuring their oxygen use. Waste heat recovery is a process that captures excess heat that would normally be discharged at manufacturing facilities and converts it into electricity and steam, or returns energy to the manufacturing process in the form of heated air, water, glycol, or oil. Basal Metabolic Rates (BMR): OrganĮnergy consumption is directly proportional to oxygen consumption because the digestive process is basically one of oxidizing food. ![]() Athletes have a greater BMR due to this last factor. The BMR is a function of age, gender, total body weight, and amount of muscle mass (which burns more calories than body fat). About 75% of the calories burned in a day go into these basic functions. Of course, during vigorous exercise, the energy consumption of the skeletal muscles and heart increase markedly. The largest fraction goes to the liver and spleen, with the brain coming next. ![]() Recycling programs are managed at the state and local levelfind information on recycling in your community. The total energy conversion rate of a person at rest is called the basal metabolic rate (BMR) and is divided among various systems in the body, as shown in Table. Reduce, Reuse, Recycle Learn how reducing, reusing, and recycling can help you, your community, and the environment by saving money, energy, and natural resources. Phantom power, also called standby power, refers to the energy thats wasted around your home when devices are plugged in and using power, but youre not. This shows how difficult it can be to define the phrase ' environmental. The rate at which the body uses food energy to sustain life and to do different activities is called the metabolic rate. after all, pollution represents wasted materials and wasted energy. ![]()
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