Question

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Answer 1

$E_c=5000 mJ=5 J\\E_c=\frac{mv_o^2}{2}=>v_o^2=\frac{2E_c}{m}=\frac{2*5}{0,1}=100=>v_o=\sqrt{100}=10 m/s\\ \vec{G}+\vec{F_f}+\vec{N}=m\vec{a}\\Ox:-F_f=ma\\Oy:N-mg=>N=mg\\F_f=\mu N=\mu mg\\-\mu mg=ma|:m=>a=-\mu g=-0,2*10=-2 m/s^2\\v=v_o+a\tau=10-2*3=10-6=4 m/s=\frac{4*1000 mm}{s}=4000 mm/s\\v=4000 mm/s->A)$