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I need a bit of help with D'Alembert's principle, I'm after the equations to find the power in a car ascending a slope with fritional resistance. The example I will give is not my assignment question as I want to work that out for myself, but an example from a textbook that just gives me the answers and not the equations, but I cannot find a way using KE and PE to get it right.

A car of mass 800kg accelerates from rest to a speed of 50km/h in 10 seconds, while ascending an incline of 1 in 70. The rolling resistance is 150N. Assuming uniform acceleration, what is

1 the power developed at 30 km/h and

2 the tractive effort

Answer to number 1 is 11.4KW, number 2 is another baffling question I’m afraid.

I have worked out that the acceleration is 1.389m/s and the distance travelled is 13.89

Any help gratefully received

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# Homework Help: D'Alembert's principle Help

**Physics Forums | Science Articles, Homework Help, Discussion**