proszę o pomoc testowe zadanie 143 i 144

[latex]ZAD.140[/latex] W tym przypadku: -Im większe tarcie, tym mniejsza siła. -Im większa masa, tym większa siła. -Im większe przyspieszenie, tym większa siła. -Dwa razy większa powierzchnia daje dwa razy większe tarcie W skrócie : [latex]F= frac{mg}{2f} [/latex] [latex]ODP.:C[/latex] ---------------------------------------------------------------------------------------------------------------------------- [latex]ZAD.141[/latex] [latex]cos alpha = frac{Fx}{F} <=> Fx=Fcos alpha [/latex] [latex]T=Fx*f=Fcos alpha *f[/latex] [latex]ODP.:C[/latex] ---------------------------------------------------------------------------------------------------------------------------- [latex]ZAD.142[/latex] [latex]ODP.:A[/latex] ---------------------------------------------------------------------------------------------------------------------------- [latex]ZAD.143[/latex] [latex] left { {{sin alpha = frac{F_y}{F} } atop {cos alpha = frac{F_x}{F} }} ight. [/latex] [latex] left { {{F_y=Fsin alpha } atop {F_x=Fcos alpha }} ight. [/latex] [latex]T=F_N*f=(F_g-F_y)f=(mg-Fsin alpha)f=[/latex] [latex]=(2kg*10 frac{m}{s^2}-10N*sin30^o)*0,2= 3N[/latex] [latex]ODP.:B[/latex] ---------------------------------------------------------------------------------------------------------------------------- [latex]ZAD.144[/latex] [latex]F_a=F_g-F_{op}=mg-F_{op}=4kg*10 frac{m}{s^2}-8N=32N [/latex] [latex]F_a*h= frac{mV^2}{2} [/latex] [latex] frac{2F_a*h}{m} =V^2[/latex] [latex]V= sqrt{frac{2F_a*h}{m}} [/latex] [latex]V= sqrt{frac{2F_a*h}{m}}= sqrt{ frac{2*32N*100m}{4kg}}=40 frac{m}{s} [/latex] [latex]ODP.:B[/latex] ---------------------------------------------------------------------------------------------------------------------------- [latex]ZAD.145[/latex] [latex]F=mgsin alpha [/latex] [latex]m= frac{F}{gsin alpha } [/latex] [latex]m= frac{F}{gsin alpha }= frac{15N}{10 frac{m}{s^2}*sin30^o }=3kg[/latex] [latex]ODP.:C[/latex] ---------------------------------------------------------------------------------------------------------------------------- [latex]ZAD.146[/latex] [latex]t= sqrt{ frac{2S}{a}}[/latex] [latex]S=frac{h}{sin alpha}[/latex] [latex]a=gsin alpha [/latex] [latex]t= sqrt{ frac{2S}{a}}= sqrt{ frac{2h}{gsin alpha*sin alpha}}= sqrt{ frac{2h}{g*sin^2 alpha } }= [/latex] [latex]= sqrt{ frac{2*20m}{10 frac{m}{s^2}*sin^230^o }}=4s[/latex] [latex]ODP.:B[/latex]   ---------------------------------------------------------------------------------------------------------------------------- [latex]ZAD.147[/latex] [latex]frac{a_1}{a_2}= frac{gsin alpha -gfcos alpha }{gsin alpha _2 -gfcos alpha_2}= frac{sin alpha -fcos alpha }{sin alpha _2-fcos alpha_2}=[/latex] [latex]=frac{sin 30^o - frac{1}{2} cos 30^o }{sin 60^o-frac{1}{2}cos 60^o}= frac{frac{1}{2}- frac{1}{2}*frac{ sqrt{3} }{2} }{frac{ sqrt{3} }{2}-frac{1}{2}*frac{1}{2} }= frac{1- frac{ sqrt{3} }{2} }{ sqrt{3}- frac{1}{2} } [/latex] [latex]ODP.:B[/latex]