10판/4. 2차원운동과 3차원운동

4-20 할리데이 10판 솔루션 일반물리학

짱세디럭스 2020. 7. 6. 05:16
{Ay=30[m]vA=3.0i^[m/s]vB0=0aB=0.40[m/s2]\begin{cases} A_y&=30\ut{m}\\ \vec v_A&=3.0\i\ut{m/s}\\ \vec v_{B0}&=0\\ \abs{\vec a_{B}}&=0.40\ut{m/s^2}\\ \end{cases} rA=ΔrA+rA0=vA ⁣dt+rA0=3i^ ⁣dt+30j^[m]=3ti^+30j[m] \begin{aligned} \vec r_A &=\Delta \vec r_A + \vec r_{A0}\\ &=\int \vec v_A\dd t+\vec r_{A0}\\ &=\int 3\i\dd t+30\j\ut{m}\\ &=3t\i+30j\ut{m}\\ \end{aligned} aB=25sinθi^+25cosθj^[m/s2] \vec a_B = \frac{2}{5}\sin\theta\i+\frac{2}{5}\cos\theta\j\ut{m/s^2} vB=vB0+aBt=25tsinθi^+25tcosθj^[m/s] \begin{aligned} \vec v_B&=\vec v_{B0}+\vec a_B t\\ &=\frac{2}{5}t\sin\theta\i+\frac{2}{5}t\cos\theta\j\ut{m/s} \end{aligned} rB=ΔrB+rB0=vB ⁣dt=25tsinθi^+25tcosθj^ ⁣dt=15t2sinθi^+15t2cosθj^[m] \begin{aligned} \vec r_B&=\Delta \vec r_B+\vec r_{B0}\\ &=\int \vec v_B \dd t\\ &=\int \frac{2}{5}t\sin\theta\i+\frac{2}{5}t\cos\theta\j \dd t\\ &=\frac{1}{5}t^2\sin\theta\i+\frac{1}{5}t^2\cos\theta\j\ut{m}\\ \end{aligned} [A, B Meet on y]\title{A, B Meet on y} 30=15t2cosθ30=\frac{1}{5}t^2\cos\theta t=56secθ[sec]t=5\sqrt{6\sec\theta}\ut{sec} [A, B Meet on x]\title{A, B Meet on x} 3t=15t2sinθ3=15tsinθ=15(56secθ)sinθ \begin{aligned} 3t&=\frac{1}{5}t^2\sin\theta\\ 3&=\frac{1}{5}t\sin\theta\\ &=\frac{1}{5}\(5\sqrt{6\sec\theta}\)\sin\theta\\ \end{aligned} θ=π3[rad]1.047197551196598[rad]1.0[rad] \begin{aligned} \theta&=\frac{\pi}{3}\ut{rad}\\ &\approx1.047197551196598\ut{rad}\\ &\approx1.0\ut{rad}\\ \end{aligned}