204 Energy and Energy TransferSection 7.9Energy and the AutomobileP7.44At a speed of 26.8 m/s (60.0 mph), the car described in Table 7.2 delivers a power of P118 3=. kW tothe wheels. If an additional load of 350 kg is added to the car, a larger output power ofPP21=+(power input to move 350 kg at speed v)will be required. The additional power output needed to move 350 kg at speed vis:∆∆out==fvmgvrbg bgµ.Assuming a coefficient of rolling friction of r=00160., the power output now needed from theengine is00160 350980268183147=+.....bgejkgm sm skWkW2.With the assumption of constant efficiency of the engine, the input power must increase by thesame factor as the output power. Thus, the fuel economy must decrease by this factor:fuel economyfuel economykm Lbg212118 318 3 1 47640
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This note was uploaded on 12/14/2011 for the course PHY 203 taught by Professor Staff during the Fall '11 term at Indiana State University .