Question

please help me .....

Answer 1

$(1) \text{Potential energy of spring}=\text{Kinetic energy of car} \\=\frac{1}{2}mv^2=\frac{1}{2}\cdot0.15\cdot10\cdot10=7.5 J\\(2) \text{75 percent Potential energy of spring}=\text{Kinetic energy of stone}=\frac{1}{2}mv^2\\\Rightarrow P.E=\frac{1}{2}\cdot0.1\cdot30\cdot30\cdot\frac{100}{75}\\=60J\\(3) \frac{{K.E}_{A}}{{K.E}_{B}}=\frac{\frac{1}{2}{m}_{A}{{v}_{A}}^{2}}{\frac{1}{2}{m}_{B}{{v}_{B}}^{2}}\\=\frac{\frac{1}{2}\cdot20\cdot1\cdot1}{\frac{1}{2}\cdot1\cdot20\cdot20}\\=\frac{1}{20}\\(4)\text{Kinetic energy of bullet}=\text{Kinetic energy of wooden target}\\\Rightarrow \frac{1}{2}\cdot0.2\cdot200\cdot200=\frac{1}{2}\cdot5v^2\\\Rightarrow v=40 \frac{m}{s}$