The truck has a mass of 50 Mg when empty. When it is unloading 5 m3 of sand at a constant rate of 0.8 m3 >s, the sand flows out the back at a speed of 7 m>s, measured relative to the truck, in the direction shown. If the truck is free to roll, determine its initial acceleration just as the load begins to empty. Neglect the mass of the wheels and any frictional resistance to motion. The density of sand is rs = 1520 kg>m3.