2 1. A van of mass 900 kg is moving along a straight horizontal road. At the instant when the speed of the van is v m s−1, the resistance to the motion of the van is modelled as a force of magnitude (500 + 7v) N. When the engine of the van is working at a constant rate of 18 kW, the van is moving along the road at a constant speed V m s−1 (a) Find the value of V. (5) Later on, the van is moving up a straight road that is inclined to the horizontal at an angle θ , where sin θ = 1 21 At the instant when the speed of the van is v m s−1, the resistance to the motion of the van from non-gravitational forces is modelled as a force of magnitude (500 + 7v) N. The engine of the van is again working at a constant rate of 18 kW. (b) Find the acceleration of the van at the instant when v = 15 (4) _____________________________________________________________________________________ _____________________________________________________________________________________ _____________________________________________________________________________________ _____________________________________________________________________________________ _____________________________________________________________________________________ _____________________________________________________________________________________ _____________________________________________________________________________________ _____________________________________________________________________________________ _____________________________________________________________________________________ _____________________________________________________________________________________ _____________________________________________________________________________________ _____________________________________________________________________________________ _____________________________________________________________________________________ _____________________________________________________________________________________ _____________________________________________________________________________________ _____________________________________________________________________________________ _____________________________________________________________________________________ _____________________________________________________________________________________ _____________________________________________________________________________________ _____________________________________________________________________________________ _____________________________________________________________________________________ _____________________________________________________________________________________