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3.4 3.5 Tutorial 2 A passenger car weighs 12.45 kN (2800 Ib), including the four tires. Each of the tires has an effective diameter of 67 cm (2.2 ft) and a radius of gyration of 27.9 cm (11 in), and weighs 222.4 N (50 Ib). The engine develops 44.8 kW (60 hp) at 4000 rpm, and the equivalent weight of the rotating parts of the driveline at engine speed is 444.8 N (100 Ib) with a radius of gyration of 10 cm (4 in.). The transmission efficiency is 88% and the total reduction ratio of the driveline in the second gear is 7.56 to 1. ‘The vehicle has a frontal area of 1.67 m’ (18 ft’) and the aerodynamic drag cocfficient is 0.45. The average cocfficient of rolling resistance is 0.015. Calculate the acceleration of the vehicle on a level road under these conditions. A passenger car weighs 20.02 kN (4500 Ib) and has a wheelbase of 279.4 cm (110 in.). The center of gravity is 127 cm (50 in.) behind the front axle and 50.8 cm (20 in.) above ground level. In practice, the vehicle cncounters a variety of surfaces, with the coefficient of road adhesion ranging from 0.2 to 0.8 and the coefficient of rolling resistance of 0.015. To prevent the loss of directional stability on surfaces with a low coefficient of adhesion under emergency braking conditions, what would you recommend regarding the braking effort distribution between the front and rear axles?
