A proton in an accelerator detector collides head-on with a stationary alpha particle, as shown in Figure 9a and Figure 9b. After the collision, the alpha particle travels at a speed of \(4.0 \times 10^6 \text{ m s}^{-1}\). The proton rebounds at \(6.0 \times 10^6 \text{ m s}^{-1}\). Find the speed of the proton before the collision, modelling the mass of the alpha particle, \(4m\), to be equal to four times the mass of the proton, \(m\). Show your working. Ignore relativistic effects. (3 marks) --- 5 WORK AREA LINES (style=lined) ---