Question

O masina parcurge 20% dintr o distanta cu viteza v1=50,4km/h,iar restul cu viteza v2=1,6xv1. Viteza medie a masinii pe intregul traseu este egala cu ?
+ mod de rezolvare va rog

Answer 1

d₁=20%d=2d/10=d/5

d₁+d₂=d<=>d/5+d₂=d=>d₂=d-d/5=4d/5

v₂=1,6v₁=1,6*50,4=80,64 km/h

t₁=d₁/v₁=d/5/v₁=d/5v₁

t₂=d₂/v₂=4d/5/v₂=4d/5v₂

t=t₁+t₂

vm=d/t=d/(d/5v₁+4d/5v₂)=d/d(1/5v₁+4/5v₂)=1/(v₂+4v₁)/5v₁v₂=5v₁v₂/(v₂+4v₁)=5*50,4*80,64/(80,64+4*50,4)=20321,28/282,24=72 km/h