PROB 3.1 A vehicle weighs 20.02 kN (4500 lb) and has a wheelbase of 279 Acm (110 in.). The center of gravity is 127 cm (50 in.) behind the front axle and 50.8 cm (20 in.) above ground level. The frontal area of the vehicle is 2.32 m (25 ft) and the aerodynamic drag coefficient is 0.45. The coefficient of rolling resistance is given by fr = 0.0136 +0.4 x 10 V, where V is the speed of the vehicle in kilometers per hour. The rolling radius of the tires is 33 cm (13 in.). The coefficient of road adhe- sion is 0.8. Estimate the possible maximum speed of the vehicle on level ground and on a grade of 25% as determined by the maximum tractive effort that the tire-road contact can support if the vehicle is (a) rear-wheel drive, and (b) front-wheel-drive. Plot the resultant resistance versus vehicle speed, and show the maximum thrust of the vehicle with the two types of drive. 3.2 The vehicle described in Problem 3.1 is equipped with an engine having torque-speed characteristics as shown in the following table. The gear ratios of the gearbox are first, 4.03; second, 2.16; third, 1.37; and fourth, 1.0. The gear ratio of the drive axle is 3.54. The transmission efficiency is 88%. Estimate the maximum speed of the vehicle on level ground and on a grade of 25% as determined by the tractive effort that the engine torque with the given transmission can provide if the vehicle is rear-wheel-drive. Plot the vehicle thrust in various gears versus vehicle speed. Engine Characteristics Engine speed, rpm 500 1000 1750 2500 3000 3500 4000 4500 5000 Engine torque, N-m 339 379.7 406.8 393.2 363.4 325.4 284.8 233.2 189.8