Question

Катер прошёл 1/4 часть пути со скорость v ,a остальную часть со скоростью 2v.определите среднюю скорость катера

Answer 1

вот......................................................

Answer 2

$v_{sr}=dfrac{l_{1} +l_{2}}{t_{1}+t_{2}}=dfrac{l}{t_{1}+t_{2}}\l_{1} =dfrac{1}{4}l, \l_{2} =l-dfrac{1}{4}l=dfrac{3}{4}l\t_{1} =dfrac{l_{1} }{v} =dfrac{1l}{4v}=dfrac{2l}{8v}\t_{2} =dfrac{l_{2} }{2v} =dfrac{3l}{8v} \v_{sr}=dfrac{l}{t_{1}+t_{2} }=dfrac{l}{dfrac{2l+3l}{8v} } =dfrac{l}{dfrac{5l}{8v}} =dfrac{l*8v}{5l}=dfrac{8}{5}v=1,6v$

Ответ: $1,6v$