One for the mathematicians:

What sort of distance would there be between two cars 60-100mph if one was one second quicker (ie 60-100mph 7sec v's 6sec)..?

I know 1 second at 100mph = aprox 150 feet, but this isn't as simple as that..

 

speed = distance over time so revert it

average speed (ish!) is 100 + 60 / 2 = 80

80mph = distance / 1 second

80 / 60 (minutes in an hour) = 1.333333 miles per minutes

1.333333 / 60 (seconds in a minute) = 0.0222222 miles per second

0.0222222 miles I think? 35.76 metres... (about 117.32 feet)

 

Same answer by another route, using school physics from rather a long time ago

v=u+at where v=final velocity, u=initial velocity, a=acceleration and t=time.

Using this formula we can work out accelaration for both cars.

v^2=U^2 + 2as, so we can use this to work out distance travelled and subtract the two to get the same answer (35.76m).

Tilly's way is easier tho!!

 

Cheers guys..

You remember school physics better than I can, I must be a LOT older..

 

Assuming both cars are doing 60mph at start and have linear acceleration (not the case in real life) then after 6 secs:
Faster car is doing 100mph and has traveled 215m (to nearest m)
Slower car is doing 94.29mph and has traveled 207m (to nearest m)
So distance between is about 8m.

 

Darn - you're right. And I got an A in A-level Physics and a B in maths I shall go to the bottom of the class immediately.

I calculated the distance car A had travelled at 6 seconds, and the distance car B had travelled at 7 seconds, which is not a lot of use. That's why I failed my S-levels

Having re-calculated it, the difference is 7.66m assuming, as you say, the acceleration is linear.

Not quite 2 car lengths.

 

1.) Average Speed of the fast car over the 6 seconds is 80mph or 60+((100-60) / 2) so distance of fast car in 6 seconds = 214.58 meters.

2.) If everything is Linear, then the speed of the slow car at 6 seconds is 94.28571 or ((100 / 7) * 6) and therefore the average speed over 6 seconds is 77.142855 or 60+((94.28571-60)/2) so distance of slow car in 6 seconds = 206.92

3.) 214.58 - 206.92 = 7.66 meters to be precise.

This is the right answer, the others are wrong. (appart from the 8m version which I agree with (although mine is more accurate. lol )

Just remember that this is linear accelleration and as in normal life there would be slight curves, then the answer would most probably be closer to 7 meters.

 

HAHAHAHA. Look at the post times. OMG that is spooky 7.66 both at the same time. LOL

 

And, what's worse, we're both sad gits to be working it out at 11.30 at night

 

I wasn't going to do it, but it started to bug me as I knew it wasn't 35meters. Done enough sprints to that speed to know.

 

I'm still trying to work it out

 

My maths teacher used to try and get us to do a "reality check" - an estimate, I guess - to see if the answer we'd calculated was in the right ballpark. Didn't do that. And I'm supposed to be an engineer too

 

You're all for slightly mistaken here.

Completely missed out that if either of the cars are a clio cup, or have neons (worse if both) that the laws of physics no longer apply.

Dave

 

Darn - you're right. I didn't even think to ask if either of the vehicles were fitted with a vent-to-air dump valve. How stupid can I get!

 

Dont really want to be picky here but the post does not say in which direction the cars were travelling in or if they started at the same time, but if we assume they are travelling in the same direction(parallel) and they started at the same time it would be:


A=v+/- t-vector B(2.33x80mph)[lat,<e=mc"> ]¬ (sxvrr#srs;2)


so Yeah about two car lengths.

 

FFS you've lost me now..!

How about this one;

If two trains leave.....?


On a serious note, would this distance be double for say a two second difference and so on..?

 

No - it's not directly proportional.

1s difference: 7.6m
2s difference: 13.4m
3s difference: 17.9m
4s difference: 21.5m

I might regret asking this, but why do you want to know?

 

A question for all you maths/physics wizards here.
If a train travelling at 100mph and weighing 300 tonnes hits a fly on the exact opposite direction the fly squashes on the train window and continues in the direction of the train, so for however short a period the fly has changed direction eg. for east to west into west to east therefore at some point it must have been stationary to reverse direction? As it was in contact with the train at this point the train must have been stationary?
I dont think I have explained this well but do you get the gist of the question?

 

The leading edge of the fly undergoes plastic deformation which accelerates the trailing edge of the fly. So the fly does spend a finite time decelerating, and accelerating, but different parts of the fly change direction at different speeds ;-)

It would be inappropriate to model the fly as a rigid body under these circumstances, you'd probably need to use something like CFD (computational fluid dynamics) to work out what happens. Sounds like overkill to me, but what would I know? :-D

 

If we could only evolve a fly that underwent elastic deformation under this scenario my car would be so much easier to clean.

 

Just interested in the sort of real world performance difference compared to the 'on paper' figures..

 

Fair enough! More useless info then...

If your Scooby does 0-60 in 5 seconds, it will have travelled about 67m in this time. If you indulge in a traffic-light grand prix - on a private road of course - then this is the lead you'll have on cars with lesser 0-60 times than you:

0-60=6s; lead=11m
0-60=7s; lead=19m
0-60=8s; lead=25m
0-60 greater than 8s...why did you bother in the first place

 

What about those with better 0-60times? How much will you be behind

 

Well, you've asked...

4.5s -> 7.5m behind
4.0s -> 17m behind
3.5s -> 29m behind
<3.5m (see answer for >8s)

I'll get my coat...

 

Very good..!

It's just that in real world conditions people are often surprised with the difference between cars that, on paper anyhow, are in different performance leagues.

You hear it all the time on here about a hot hatch that 'stayed in touch' with a 300bhp scoob and conversely a 300bhp scoob that stayed with a 'supercar'.

Given the figures you so kindly supplied, showing the relatively small distances involved, it's no wonder these things happen. Especially when you factor in driver response/hesitation/ability..

As I have said in other threads, it takes a car with a big performance advantage to 'trounce/leave for dead' another car.

Interesting IMHO..

 

Well, for my next trick, I'll calculate the air-speed velocity of a laden sparrow