Răspuns:
Explicație:
[tex]1.13.1\\F = 50 N\\\Delta x = 100 m\\L = F \cdot \Delta x = 50 N \cdot 100 m = 5000 J\\E_c = L = 5000 J\\1.13.2\\F_r = 200 N\\\Delta x_m = 50 m\\E_c = L = F_r \cdot \Delta x_m = 200 N \cdot 50 m = 10000 J\\1.13.4\\E_{ci} = 22500J\\E_{cf} = 50000J\\\Delta x = 200 m\\a)L =F \cdot \Delta x= E_{cf} - E_{ci} => F = \frac{ E_{cf} - E_{ci}}{\Delta x} \\F = \frac{50000J - 22500J}{200m} = 137.5 N\\b)\\F_f = f \cdot F \\L = F \cdot \Delta x\\L_f = F_f \cdot \Delta x = f \cdot F \cdot \Delta x\\[/tex]
[tex]L - L_f = E_{cf} - E_{ci} =>F \cdot \Delta x - f \cdot \ F \cdot \Delta x = E_{cf} - E_{ci}\\F (\Delta x - f \cdot \Delta x) = E_{cf} - E_{ci}\\F = \frac{E_{cf} - E_{ci}}{\Delta x - f \cdot \Delta x} \\F = \frac{50000J - 22500J}{200m - 0.01\cdot 200m}\\ F = \frac{27500J}{198m}\\ F= 138.8 N[/tex]
