6. A motor car, of a total mass 1400 kg, running in top gear at 55...

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Mechanical Engineering

6. A motor car, of a total mass 1400 kg, running intop gear at 55 km/h, passes on to a rsing gradient of 1 in 20 atthat speed. The road and other resistances may be taken as constantat 270 N/t. With condition unchanged, the speed falls uniformly to40 km/h in a distance of 360 m. An intermediate gear is thenengaged for which the speed ratio between the engine and the roadwheels is 9:1 and the transmission efficiency is 85 per cent. Theengine is then developing a torque of 85 Nm
Determine;
a. The tractive effort before and after the gear change, given thatthe road wheels are 750 mm diameter, [851 N; 1735 kN]
b. The time between the start of retardation and the recovery ofthe original speed of 55 km/h and [36 s]
c. The power being developed by the engine when the car isretarding and accelerating through 50 km/h, given that thetransmission efficiency in top gear is 94 percent.Â Â Â Â Â Â Â Â [12.56 kW;28.35 kW]

Answer & Explanation Solved by verified expert

3.9 Ratings (377 Votes)

Initial velocity u 55 kmh 1528 msFinal velocity v 40 kmh 1111 msUsing v2 u2 2as we get11112 15282 2 a 360Acceleration a 01527 ms2Grade Tan 1 20Angle 2862 degForce due to gravity in the direction See Answer

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