题目
PHYS 114 B Tutorial practice 7 - Conservation of Energy
多重下拉选择题
In your notebook, write an expression for each of the following quantities in terms of the given variables and any physical constants. If any of these are zero, state so explicitly. the change in kinetic energy of system BE is not zero the change in potential energy of system BE is not zero the net external work by external forces on system BE is zero Write an equation that relates the three expressions above.
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思路分析
Question restatement:
- You are asked to write an expression for each of the following quantities in terms of the given variables and any physical constants, noting explicitly if any are zero:
1) the change in kinetic energy of system BE
2) the change in potential energy of system BE
3) the net external work by external forces on system BE
- Then you should write an equation that relates the three expressions above.
Option by option analysis:
Option A: the change in kinetic energy of system BE is not zero
- In classical mechanics, the work-energy principle states that the net external work on a system equals the change in its kinetic energy: ΔK = W_ext. This means that if W_ext is zero, then ΔK must be zero as well. Therefore, claiming ΔK is not zero generally implies that there is some nonzero net external work being done on the system. If the third quantity (net external work) is explicitly stated to be zero, then this option cannot be true under that condition, because W_ext = 0 would force ΔK = 0. If you are treating the three quantities as interrelated expressions, you should recognize that ΔK and W_ext are directly linked by ΔK = W_ext, so they cannot be independently no......Login to view full explanation登录即可查看完整答案
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