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heavenjai2007
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Homework Statement
A vehicle engine has a power output of 6.2 KW and uses fuel which releases 45 MJ per kilogram when burned. At a speed of 30ms ^-1 on a level road, the fuel usage of the vehicle is 18km per kilogram. Calculate: the useful energy supplied by the engine in this time.
Homework Equations
efficiency= (useful energy) / (energy supplied)
The Attempt at a Solution
Well, first i know that the time taken by the vehicle to travel 18 km at 30ms^-1 is 600s using s=d/t. i also know that (useful energy) is equal to (mg x change in height). the problem is that I am not given the value of mg(N) therefore i have to work it out. so i know F=mxa but again, we're not given the value of m and a. i might have confused my self.