Acceleration question:

How many G's do you have to do of constant acceleration to get the time through a quarter mile down to 2 seconds or less?

Originally posted by sonhouse
How many G's do you have to do of constant acceleration to get the time through a quarter mile down to 2 seconds or less?

d = di + vi*t + (1/2)at^2

That's correct, isn't it?

(1/4)mi = 0 + 0 + (1/2)a(4s^2)
mi = 8s^2 * a
mi/(8s^2) = a

So we need an acceleration of 1/8 mi/s^2

One G is 32 ft/s^2

(1/8)(mi/s^2)*(5280 ft/mi) = 660 ft/s^2

~20.6 G's

Originally posted by AThousandYoung
d = di + vi*t + (1/2)at^2

That's correct, isn't it?

(1/4)mi = 0 + 0 + (1/2)a(4s^2)
mi = 8s^2 * a
mi/(8s^2) = a

So we need an acceleration of 1/8 mi/s^2

One G is 32 ft/s^2

(1/8)(mi/s^2)*(5280 ft/mi) = 660 ft/s^2

~20.6 G's

I did that question because I put the formulae up in the other post!
A=2S/(T squared)
Thats all there is too it.
1/4 mile = 1320 ft so times 2=2640/4=660 Ft/sec squared, divide by 32=20.625.
You just assume starting from zero velocity, simplifies the equation.

Originally posted by sonhouse
I did that question because I put the formulae up in the other post!
A=2S/(T squared)
Thats all there is too it.
1/4 mile = 1320 ft so times 2=2640/4=660 Ft/sec squared, divide by 32=20.625.
You just assume starting from zero velocity, simplifies the equation.

I know. I'm the kind of guy who likes to start with unsimplified equations and then simplify them; for example, I use Ideal Gas Law even if Boyle's Law will do the job.

I'm surprised that engineers in US is still using feet and miles. It's like a duck pond with their own units stubbornly used.
Whats wrong with SI-units, as used in the rest of the civilised world?

How about NASA, they have started using the international measuring system, don't they?

Originally posted by FabianFnas
I'm surprised that engineers in US is still using feet and miles. It's like a duck pond with their own units stubbornly used.
Whats wrong with SI-units, as used in the rest of the civilised world?

How about NASA, they have started using the international measuring system, don't they?

It's mostly habit and infrastructure issues at this point. Yes, NASA's on SI, and the different units actually caused problems for some rover or something.

Originally posted by AThousandYoung
It's mostly habit and infrastructure issues at this point. Yes, NASA's on SI, and the different units actually caused problems for some rover or something.

Yes, I read something about that. Some mixup between inch and centimeters, wasn't it?

At university level, what kind of units are used, nowadays?

England switched to decimal system in some respect, Australia has done it. How much progress is US doing?

Noone thinks that 100 cents on a dollar is awkward. On the other hand everone accepts 60 minutes an hour... 😕

Originally posted by FabianFnas
Yes, I read something about that. Some mixup between inch and centimeters, wasn't it?

At university level, what kind of units are used, nowadays?

England switched to decimal system in some respect, Australia has done it. How much progress is US doing?

Noone thinks that 100 cents on a dollar is awkward. On the other hand everone accepts 60 minutes an hour... 😕

They tried to change the clocks, but it never caught on.

In science we use SI. In engineering they use Imperial (feet).

Originally posted by AThousandYoung
They tried to change the clocks, but it never caught on.

In science we use SI. In engineering they use Imperial (feet).

This means that I can tell an engineer from a scientist bu just asking him how tall he is?
Does he answer 6 foot 8, then he is an engineer. Does he answer 180 centimeter, then he is a scientist. Does he answer 4 gallon, he is... eh, what?

How tall are you, AThousandYoung?

Originally posted by FabianFnas
I'm surprised that engineers in US is still using feet and miles. It's like a duck pond with their own units stubbornly used.
Whats wrong with SI-units, as used in the rest of the civilised world?

How about NASA, they have started using the international measuring system, don't they?

I put it in miles because the standard drag race in the us is the quarter mile. Imagine this conversation:
Well Bubba, how does that thing run in the 402.34?
HUH, wat de haill you talkin bout?
402.34 meters hogbreath, its a quarter mile. Jeesh.

England now uses SI units at university level for all it's science. In fact, in England SI units are used all throughout primary and secondary school aswell (I think primary school is equivelent to elementary school and secondary is equivelent to high school, but not sure.)

Also, SI units are used pretty much everywhere in England. All transactions need to be in SI units because of the European Union laws, it caused some upset when it happened but is now widely accepted.

Saying this though, the older generation (my parent's generation) are not so good at using SI units. They still work in Imperial units for most things (like mass and distance), but this will change as the new generation are never exposed to the old units.

The one exception is road signs; distances on road signs are in miles, not km.

Originally posted by MattP
England now uses SI units at university level for all it's science. In fact, in England SI units are used all throughout primary and secondary school aswell (I think primary school is equivelent to elementary school and secondary is equivelent to high school, but not sure.)

Also, SI units are used pretty much everywhere in England. All transactions need to e old units.

The one exception is road signs; distances on road signs are in miles, not km.

Maybe the US should join the EU...
Let's see, EUUS USEU SUUE...

Originally posted by sonhouse
Maybe the US should join the EU...
Let's see, EUUS USEU SUUE...

Joint Europe States United States - JESUS - Oh no...

Originally posted by FabianFnas
Joint Europe States United States - JESUS - Oh no...

Or Bush Lead European Democracy. BLED.