Hi,

 

There was a recent post entitled "Maths Homework" about 0-60 times and 1/4 mile times. Well it set me thinking as follows.

 

With a standing start, given the distance, 1/4 mile, and the time, say between 10 and 20 seconds, you can easily work out the what constant acceleration is needed, (Techies see note 1).

 

The big assumption here is constant acceleration, clearly the acceleration will vary over the 1/4 mile, but humor me for a while.

 

From the acceration you can easily work out both the 0-60 time and the final speed, (note 2), from which you can work out the kinetic energy, (note 3). Now this amount of energy has to be supplied by the engine in the specified time and so you can calculate the Power needed, (note 4).

 

Here are the results for a 1500 kg car, (300zx?)

 

Time HP 0 to 60

10 651 3.34

11 489 4.04

12 377 4.80

13 296 5.64

14 237 6.54

15 193 7.50

16 159 8.54

17 133 9.64

18 112 10.81

19 95 12.04

20 81 13.34

 

To repeat, the big assumption here is constant acceleration but all in all the numbers seem to stack up so what about the E36 M3, soft-top?

 

Weight is 1635 kg so recalculate to get ...

 

Time HP 0 to 60

10 710 3.34

11 533 4.04

12 411 4.80

13 323 5.64

14 259 6.54

15 210 7.50

16 173 8.54

17 144 9.64

18 122 10.81

19 103 12.04

20 89 13.34

 

The specification I saw stated 0 - 100 kmph, (very close to 60 mph) 5.6s and Max Power 236 KW = 316 HP so my table would suggest about 13 seconds for the 1/4 mile, and the bloke claimed 12.5 sec .

 

Bearing in mind the assumptions a reasonable result.

 

Zimon

 

 

Note 1.

For a standing start

 

Distance = Acceleration * Time * Time /2

 

Note 2.

From a standing start

 

Final Speed = Acceleration * Time

 

Note 3.

 

Kinetic Energy = Mass * Speed * Speed /2

 

Note 4.

 

Power = Energy / Time

OOPS used TAB rather than spaces, so here are the tables again

 

1500 kg car, (300zx)

 

Time HP 0 to 60

10 651 3.34

11 489 4.04

12 377 4.80

13 296 5.64

14 237 6.54

15 193 7.50

16 159 8.54

17 133 9.64

18 112 10.81

19 95 12.04

20 81 13.34

 

Weight is 1635 kg so recalculate to get ...

 

Time HP 0 to 60

10 710 3.34

11 533 4.04

12 411 4.80

13 323 5.64

14 259 6.54

15 210 7.50

16 173 8.54

17 144 9.64

18 122 10.81

19 103 12.04

20 89 13.34

 

 

Zimon

Bugger, spaces and tabs get compressed sorry - moderators may wish to delete both this and the second attempt to format the tables.

Yeah, I've noticed this in the past, a real annoyance. Could try a different (non-proportional?) font.

 

 

Originally posted by Zimon

Bugger, spaces and tabs get compressed sorry - moderators may wish to delete both this and the second attempt to format the tables.

10 710 3.34

 

Experiment with courier new

Experiment failed - it must be a html/forum thing

Originally posted by Zimon

Experiment failed - it must be a html/forum thing

 

Don't worry.........it wasn't very interesting anyway.

 

 

(joke!) :D :D :D

Woops, I've only just seen this. It was my maths homework... really it was just a comment on what nobs some people are. So it went like: nob reckons he can do a 12.5 sec 1/4. But also reckons his 0-60 had dropped to 8 secs (did I say 8 originally?) because he's got a 10-ton sound system.

 

Showing all working out, and using diagrams where appropriate, prove scientifically: this bloke is a bull-sh*tting bell-end.

 

He probably never even ran the car. He probably just looked up some 1/4 figures hoping to make his story sound "believable".

 

Never mind. Interesting numbers tho.

51x,

 

What amazed me was how accurate the tables turned out. I have compared them against MR2 MX5 Boxter specifications and they stack up!