Độ biến thiên động năng:
\(A_c=\Delta W=W_2-W_1=\dfrac{1}{2}m\left(v_B^2-v_A^2\right)\)
\(\Rightarrow F_c\cdot s=\dfrac{1}{2}m\left(v_B^2-v_A^2\right)\)
\(\Rightarrow\left(F-F_{ms}\right)\cdot s=\dfrac{1}{2}\cdot2\cdot1000\cdot\left(v_B^2-0\right)\)
\(\Rightarrow\left(5200-0,1\cdot2\cdot1000\cdot10\right)\cdot20=\dfrac{1}{2}\cdot2\cdot1000\cdot v_B^2\)
\(\Rightarrow v_B=8\)m/s
Xe đi lên mặt phẳng nghiêng:
\(A=\Delta W=W-W_B\)
\(\Rightarrow-\mu mg\cdot cos\alpha=mgs\cdot sin\alpha-\dfrac{1}{2}mv_B^2\)
\(\Rightarrow-0,1\cdot2\cdot1000\cdot10\cdot cos30^o=2\cdot1000\cdot10\cdot s\cdot sin30^o-\dfrac{1}{2}\cdot2\cdot1000\cdot8^2\)
\(\Rightarrow s=6,23m\)
