Question

Un mobil parcurge in prima jumatate de timp o distanta cu v1=80 km/h si in a doua jumatate de timp o distanta cu v2=40 km/h.Sa se afle viteza medie?

Answer 1

d₁=d/2

d₂=d/2

d₂+d₁=d

t₁=d₁/v₁=d/2/v₁=d/2v₁

t₂=d₂/v₂=d/2/v₂=d/2v₂

t=t₁+t₂

d=vm*t=>vm=d/t=d/(t₁+t₂)=d/(d/2v₁+d/2v₂)=d/[d(1/2v₁+1/2v₂)]=1/(1/2v₁+1/2v₂)=2v₁v₂/(v₁+v₂)=2*80*40/(80+40)=6400/120=53,33 km/h