**1. The problem statement, all variables and given/known data**

An auto manufacturer reports that the maximum power delivered by the engine of a car of mass 1230 kg is 92.4 kW. Find the minimum time in which the car could accelerate from rest to 29.1 m/s. In a test the time to do this is found to be 12.3 s. Account for the difference in this time.

**2. Relevant equations**

P = W/t

Work-KE theorem

**3. The attempt at a solution**

t = [itex]\frac{W}{P}[/itex]

= [itex]\frac{.5(1230)(29.1)^{2}}{92.4(10^{3})}[/itex]

= 5.64s

The difference in time is due to not accounting for friction force.

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