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huybinhs

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## Homework Statement

A car with mass 1000 kg accelerates from 0 m/s to 40 m/s in 10.0 s. Ignoring air resistance. The engine has a 22% efficiency, which means that 22% of the thermal energy released by the burning gasoline is converted into mechanical energy.

a) What is the average mechanical power output of the engine?

b) What volume of gasoline is consumed? Assume the burning of 1 L of gasoline releases 46 MJ of thermal energy.

## Homework Equations

[tex]\Delta[/tex]x = [(v + v

_{0}) * t] / 2

Power

_{avg}= work/time = energy transformed / time

Efficiency = Wout/Ein = Pout/Pin

## The Attempt at a Solution

a) [tex]\Delta[/tex]x = [(v + v

_{0}) * t] / 2

=> [tex]\Delta[/tex]x = 200 m

Work = m g x = 1000*9.81*200 = 1962 kW.

The engine has a 22% efficiency, which means that 22% of the thermal energy released by the burning gasoline is converted into mechanical energy.

Wout = 0.22 * 1962kW = 431.64 kW.

1hp = 746 W => 431.64 kW = 579 hp = WRONG answer

b) I have no ideas to start. What is MJ?

Please advise! Thanks!

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