Question

Un autovehicul cu masa m=2000kg isi mareste viteza de la v1=20m/s la v2=30m/s intr-un interval de 40 secunde. Ce valoare are forta de frecare dintre roti si asfalt, daca forta de tractiune este de 8000N?

Answer 1

[tex]\displaystyle Se~da:\\ \\ m=2000kg\\ \\ v_1=20\frac ms\\ \\ v_2=30\frac ms\\ \\ t=40s\\ \\ F=8000N\\ \\ F_{fr}=?N\\ \\ \\ Formule:\\ \\ F-F_{fr}=m\times a\\ \\ F_{fr}=F-m\times a[/tex]


[tex]\displaystyle a=\frac {\Delta v}t\\ \\ a=\frac{v_2-v_1}{t}\\ \\ \\ F_{fr}=F-m\times \frac{v_2-v_1}{t}\\ \\ \\ Calcule:\\ \\ F_{fr}=8000-2000\times \frac{30-20}{40}=7500N[/tex]