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有些物理习题用常规方法来解往往推算复杂,甚至无法解出但如果根据题意巧作假设,则可快速解答。假设有以下几种:一、过程假设【例1】将40克10℃的水、30克30℃的水、20克70℃的水混合,则混合后的温度是()A.30℃B.40℃c.50℃D.无法确定解析:此题可作过程假设。假设它们均降温至0℃后再共同升高温度△t,则有cm_1△t_1+cm_2△t_2+cm_3△t_3=c(m_1+m_2+m_3)△t,即40g×10℃+30g×30℃+20g×70℃=90g×△_t,解得△t=30℃。因此选答案A。
Some physical exercises using conventional methods to calculate the complexity of the past often projections, and even unable to solve, but if based on the trickery to make assumptions, you can quickly answer. Assume the following: First, the process assumes that [Example 1] 40 g of 10 ° C water, 30 g of water at 30 ° C and 20 g of water at 70 ° C are mixed, the temperature after the mixing is (A.) A.30 ° C .40 ℃ c.50 ℃ D. Can not be determined Analysis: This question can be used for process assumptions. Assuming that both of them are cooled to 0 ° C and then raise the temperature together, Δt, there are cm_1Δt_1 + cm_2Δt_2 + cm_3Δt_3 = c (m_1 + m_2 + m_3) Δt, that is, 40g × 10 ℃ + 30g × 30 ℃ + 20g × 70 ℃ = 90g × △ _t, solution △ t = 30 ℃. So choose answer A.