158.4 км/ч = 158.4*1000/3600 = 44 м/c
45 м/мин = 45*60/1000 = 2.7 км/ч
90 м/мин = 90/60 = 1.5 м/с
Задача на движение с рывком
![S_x=A-Bt+Ct^2-Dt^3 \medskip \\ C=5, D=1 \medskip \\ S_x=-t^3+5t^2-Bt+A \medskip \\ (S_x)''=(v_x)'=a_x \medskip \\ (S_x)'=v_x=-3t^2+10t-B \medskip \\ (v_x)'=a_x=-6t+10 \medskip \\ a_x(1)=-6\cdot 1+10=4](https://tex.z-dn.net/?f=S_x%3DA-Bt%2BCt%5E2-Dt%5E3%0A%5Cmedskip%0A%5C%5C%0AC%3D5%2C+D%3D1%0A%5Cmedskip%0A%5C%5C%0AS_x%3D-t%5E3%2B5t%5E2-Bt%2BA%0A%5Cmedskip%0A%5C%5C%0A%28S_x%29%27%27%3D%28v_x%29%27%3Da_x%0A%5Cmedskip%0A%5C%5C%0A%28S_x%29%27%3Dv_x%3D-3t%5E2%2B10t-B%0A%5Cmedskip%0A%5C%5C%0A%28v_x%29%27%3Da_x%3D-6t%2B10%0A%5Cmedskip%0A%5C%5C%0Aa_x%281%29%3D-6%5Ccdot+1%2B10%3D4)
По второму закону Ньютона:
![F=ma \medskip \\ F=0.5\cdot 4= 2](https://tex.z-dn.net/?f=F%3Dma%0A%5Cmedskip%0A%5C%5C%0AF%3D0.5%5Ccdot+4%3D+2)
Решения задач во вложениях
Дано m=0,3 кг t1=50C t2=0C Q- ?
Q=c*m*(t1-t2)=130*0,3*50=130*15=1950 Дж
2) m=2000 кг t2-t1=50C Q- ?
Q=c*m*(t2-t1)=4200*2000*50=420*10^6 Дж=420 МДж