Question

urasc fizica urasc fizica urasc fizica​

Answer 1

Răspunsul la prima problema in imagine.

Answer 2

$20.G=mg=30*10=300N\\\eta=\frac{L_u}{L_c}=\frac{G*h}{L_c}=>L_c=\frac{G*h}{\eta}=\frac{300*12}{80\%}=\frac{3600}{0,8}=4500J=>L_c=4500 J \\\\21.\vec{G}+\vec{N}+\vec{F_f}=m\vec{a}\\Ox:-F_f=ma\\Oy:N-mg=0=>N=mg\\F_f=\mu N=\mu mg\\-\mu mg=ma=>a=-\mu g\\v=0\\v^2=v_o^2+2ad<=>v^2=v_o^2-2\mu gd<=>0^2=10^2-2*0,2*10d<=>-100=-4d=>d=\frac{100}{4}=25 m=>d=25 m\\ L_F_f=-F_f*d=-(-mad)=mad=-\mu gmd=-0,2*10*2*25=-100J=>L_F_f=-100J$