Question

o barca parcurge distanta de 2km in aval in timpul t1=6 min 40 secunde iar in amonte in timpul t2=33 min 20 secunde. aflati viteza barcii fata de apa v1 (aceeasi in aval ca si in amonte ) si viteza apei fata de mal v2.

Answer 1

t1=6min40s=400s; t2=33min20s=2000s; Notam cu D distanta de 2km. In aval v=v1+v2,iar in amonte v'=v1-v2.D=vt1=t1(v1+v2)(1);D=v't2=t2(v1-v2)(2).Din relatia (1)=>v1+v2=D/t1=2000/400=5m/s(3).Din relatia (2)=>v1-v2=D/t2=2000/2000=1m/s.(4).Din relatiile (3) si (4)=>2v1=6m/s=>v1=3m/s;v2=2m/s