[latex]v_1=36 frac{km}{h} =10frac{m}{s}\ v_2=20frac{m}{s}\\ Delta v=v_2-v_1=10frac{m}{s}\\ s= frac{at^2}{2} +v_1t= frac{ frac{Delta v}{t}cdot t^2 }{2} +v_1t= frac{Delta vcdot t}{2} +v_1t\\ W=mas=1000kgcdot frac{Delta v}{t} cdot (frac{Delta vcdot t}{2} +v_1t)=\\ =1000kgcdot {Delta v} cdot (frac{Delta v}{2} +v_1)=\\ =1000kgcdot 10frac{m}{s}cdot 15 frac{m}{s} =\\ =150000J=oxed{150kJ}[/latex]
[latex]dane:\m = 1000 kg\v_1 = 36frac{km}{h}=36*frac{1000m}{3600s} = 10frac{m}{s}\v_2 = 20frac{m}{s}\ szukane:\W = ?[/latex] [latex]W = Delta E_{k}=frac{mv_2^{2}}{2}-frac{mv_1^{2}}{2}\\W = frac{m}{2}*(v_2^{2}-v_1^{2})\\W = frac{1000kg}{2}*[(20frac{m}{s})^{2}-(10frac{m}{s})^{2}]=500kg*(400-100)frac{m^{2}}{s^{2}}=500*300J\\W = 150 000 J = 150 kJ[/latex] Odp. Szukana praca ma wartość 150000 J (150 kJ).
