Answer to Question #332928 in Electrical Engineering for Utopian_brian

Question

A motor car, of total mass 1400kg, running in top gear at 55km/h, passes on to a rising of 1 in

20 at that speed. The road and other resistances may be taken as constant at 270N/t. With

conditions unchanged, the speed falls uniformly to 40km/h in a distance of 360m. An

intermediate gear is then engaged for which the speed ratio between the engine and the road

wheels is 9:1 and the transmission efficiency is 85%. The engine is then developing a torque

of 85Nm. Determine: (a) The tractive efforts before and after the gear change, given that the

road wheels are 750mm in diameter, (b) The time between the start of retardation and the

recovery of the original speed of 55km/h, and (c) The powers being developed by the engine

when the car is retarding and accelerating through 50km/h, given that the transmission

efficiency in top gear is 94%.