if a car with a 40l petrol tank which equals229.17kJ of energyuses it at a rate of 20kW, how long will it last

Answer 1

A Joule is a watt-second.
20 kWatts is 20 kJ per second
or like said before 11 seconds.
The problem is the petrol has 34-35 MegaJoules per liter of which the typical vehicle would convert 20 percent to work.
This means your tank should have 40 x 34 x 20% x 1000
or 272,000 kJoules.

Answer 2

It is not possible for a car with a petrol engine to use fuel at a constant rate, however this was the method used for testing steam locomotives on the railways where bags of coal of known weight were added to an established fire at set intervals, the train could be braked for speed restrictions and the steaming rate maintained by increasing the cut off point of steam in the cylinders with the locomotive steaming against the brakes, BR Western Region used the Line from Stoke Gifford to Swindon for testing in this manner.
Petrol engines would need incredibly complex air metering units to match air input to fuel input, the reverse of what Fuel injection metering units do, would need to run on level and gently curved tracks and need incredibly complex cooling systems to achieve a stable energy use that it is completely impractical.
I think you need to understand that you know very little if anything about petrol engines and indeed about cars.
Nobody cares how long 40L of petrol lasts, except at tickover when stuck in a snowdrift 50 miles from civilisation, it is distance per litre which matters, actually not even that it is the cost in £ or $ of the fuel to drive the journeys deemed necessary by an owner within a set period which matters, otherwise the conundrum on whether to drive 50 miles in an hour using dual cariage ways or cut through town and do 25 miles albeit at half the MPG, also in an hour cuts in.
I appreciate you are trying bto look really clever and intellectual, pity you just end up looking stupid

Answer 3

229.17 kilojoules = 63.6583333 watt hours

.../20kW = 11.458 seconds

If you meant 20W rather than 20kW, it would be 3.183 hours.

Answer 4

7000 years

Answer 5

You've confused me with someone that gives a toss

Answer 6

Question does not make sense.What do you mean by ,how long?

Answer 7

till it runs out!