Salut!
O formula de calcul a randamentului, in care avem nevoie doar de masura unghiului α, respectiv valoarea coeficientului de frecare μ este:
[tex]\red{\boxed{\bf \eta = \frac{sin \alpha }{sin \alpha + \mu cos \alpha}}} \\\\\\sin \alpha = sin \ 45= \frac{\sqrt{2} }{2} \\cos \alpha = cos \ 45 = \frac{\sqrt{2} }{2} \\\\\\\eta = \frac{\frac{\sqrt{2} }{2} }{\frac{\sqrt{2} }{2}+ \frac{1}{2}(\frac{\sqrt{2} }{2}) } \\\\\eta =\frac{\frac{\sqrt{2} }{2} }{\frac{\sqrt{2} }{2}+\frac{\sqrt{2}} {4} } \\\\\eta = \frac{\frac{\sqrt{2} }{2} }{\frac{3\sqrt{2} }{4} } \\\\\eta = \frac{\sqrt{2} }{2} \times \frac{4}{3\sqrt{2} } \\\\[/tex]
[tex]\eta = \frac{2}{6} \\\\\eta = \frac{1}{3} = 33,(3)\%[/tex]
