Question

nu am stiut sa le fac pe cele incercuite 234,236. ajutor :)​

Answer 1

$34.v_2=72 km/h=20 m/s\\v_1=18 km/h=5 m/s\\v_2^2=v_1^2+2ad<=>20^2=5^2+2*125a<=>400-25=250a<=>375=250a|:250=>a=1,5 m/s^2\\v_2=v_1+at<=>20=5+1,5t<=>15=1,5t|:1,5=>t=10s\\P=\frac{L}{t}=>L=Pt=15*10=150 kJ=>L=150 kJ$

$36.p_o=mv_o\\E_c=\frac{mv_o^2}{2}=>mv_o^2=2E_c\\p=mv\\p=4p_0<=>4mv_o=mv|:m=>v=4v_o\\E_{c_o}=\frac{mv_o^2}{2}\\ E_c'=\frac{mv^2}{2}=\frac{m(4v_o)^2}{2}=\frac{16v_o^2m}{2} \\\Delta E_c=Ec'-E_{c_o}=\frac{16v_o^2m}{2}-\frac{mv_o^2}{2}=\frac{15mv_o^2}{2}=\frac{15*2E_c}{2}=15E_c=15*200= 3000J=3kJ\\\Delta E_c=L=>L=3kJ$