Vật lí (Vận tốc)

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pkagunny0408

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angleofdarkness


Thời gian đi cả đoạn AC là:
$$t=t_1+t_2=\dfrac{S_1}{v_1}+\dfrac{S_2}{v_2}= \dfrac{S}{4v_1}+\dfrac{3S}{4v_2}=\dfrac{25}{v_1}+ \dfrac{3.25}{4.2.v_1}=\dfrac{25}{v_1}+\dfrac{75}{8v_1}=0,5(h).$$

Giải ra đc $v_1=68.75;v_2=2v_1=137,5(km/h)$
 
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