solutions - Shoreline School District
Answers: 1. Initial system energy KE Eint Final system energy During PEgrav PEspring Wext Q KE Eint PEgrav PEspring Bar chart graph key KE Kinetic energy Eint Internal energy PEgrav PEspring Arbitrary height, same for both (can be zero) Wext Q Gravitational potential energy Spring potential energy Work done by external forces Heat added to system Use g = 10 m/s2 for simplicity 2. Initial system energy KE Eint Final system energy During PEgrav PEspring Wext Q KE Eint PEgrav PEspring Bar chart graph key KE Kinetic energy Eint Internal energy PEgrav Arbitrary height, same for both (can be zero) PEspring Wext Q Gravitational potential energy Spring potential energy Work done by external forces Heat added to system Use g = 10 m/s2 for simplicity 3. Answer: The bar given in the problem represents 320 Joules of work (8 bars); the final spring potential energy is 160 Joules. The work done by friction is negative 80 Joules (2 bars), and there must therefore be 320 - 80 -160 = 80 Joules of kinetic energy. Initial system energy KE Eint Final system energy During PEgrav PEspring Wext Q KE Eint PEgrav PEspring Bar chart graph key KE Kinetic energy Eint Internal energy PEgrav PEspring 80 Joules more than initial Wext Arbitrary initial height (can be zero) Q Gravitational potential energy Spring potential energy Work done by external forces Heat added to system Use g = 10 m/s2 for simplicity 4. Answer: note that some energy is changed into internal energy of the system such as heat (spring) Initial system energy KE Eint Final system energy During PEgrav PEspring Wext Q KE Eint PEgrav PEspring Bar chart graph key KE Kinetic energy Eint Internal energy PEgrav Arbitrary initial height (can be zero) PEspring Wext Q Gravitational potential energy Spring potential energy Work done by external forces Heat added to system Use g = 10 m/s2 for simplicity
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