Răspuns:
1. R² = F₁² + F₂² + 2F₁F₂cos60
R² = 100 + 900 + 2*10*30*1/2
R² = 1300
R = [tex]\sqrt{1300} [/tex] = 10[tex]\sqrt{13} [/tex] N varianta a.
Explicație:
2. 45km/h = 45 * 1000m/ 3600s = 12.5 m/s varianta c.
3.
d = 15 km = 15 000 m
t = 25 * 60 = 1500 s
v = d/t = 15000/1500 = 10 m/s
Pt. tren
v₁= 2v = 20m/s
t₁ = 10*60 = 600s
d₁ = v₁ * t₁ = 20 m/s * 600s = 12 000 m = 12 km varianta b.
