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/sci/ - Science & Math

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8289177 No.8289177 [Reply] [Original]

If a car is going 50km/hr and stops in 0.3km, how long does it take the car to stop?

>> No.8289186

>>8289177
Linear deceleration? Ignore effects of friction, aerodynamics etc.?

>> No.8289394

>>8289177
>stops in 0.3km
>how long does it take the car to stop?

I'd say 9292,4km

>> No.8289397

>>8289186
>Ignore effects of friction, aerodynamics etc.?
>implying any of that matters

>> No.8289400

>>8289177
it will take at least 21.6 seconds.

>> No.8289426

twice the time it would take to drive the 300m without stopping

>> No.8289429

>>8289397
Of course it does. The way a car breaks is heavily dependent on its tires and its shape.

>> No.8289495

>>8289177
About 0.3 km

>> No.8289503

>>8289177
~1.19882076 s

>> No.8289543
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8289543

I think it's 43.6 seconds
what am I doing wrong here?
is the half obsolete?

>> No.8289545

>>8289543
43.2*

>> No.8289578

Let's say the car halves its speed until it gets to 0.150 km then halves that speed until gets to 0.175km, then halves that speed until it gets to... etc

The car will never arrive at 0.3 in finite time

>> No.8289599

>>8289545
yup
you know:
s=a*t^2/2
and:
v=a*t
juggle:
a=2s/t^2
a=v/t
subtract:
0=2s/t^2-v/t
juggle:
v/t=2s/t^2
v*t=2s
t=2s/v=43.2 s

>> No.8289613

144 seconds

>> No.8289632

>>8289578
But if the car drives 0.1 km then 0.2 km then 0.3 km etc, it will have stopped 0.008333... km behind where it started

>> No.8289726

>>8289599
so it IS 43.2 seconds? I don't see anything wrong with my calculations

>> No.8289730

>>8289177
Bout tree fiddy

>> No.8289739

>>8289726
yes

>> No.8289741

>>8289397
>implying it doesn't
a car could crash-brake to 1 km/hr as quick as it possibly can and then bleed off velocity as slowly as it can before it stops at 0.3 km

or it could crash-brake at the last possible second

or it could uniformly decelerate

all of those will have different times

>> No.8289753

>>8289429
But >>8289186 already specified "linear deceleration", which takes care of all that variability.

>> No.8289754
File: 45 KB, 515x320, squatchya-gonna-do.gif [View same] [iqdb] [saucenao] [google]
8289754

>>8289177
>its a OP baits with a vague problem, that has multiple right solutions episode

>> No.8289778

>>8289177
1 plank time.

Enjoy your destroyed universe, faggot.

>> No.8289853

>>8289177
v=50-(50/T)t
d=50t-(25/T)t^2+C
0=50(0)-(25/T)(0)+C
0.3=50T-(25/T)T^2
T=0.012 hours = 43.2 seconds

>> No.8289858

YOU GUYS ARE SO SMART WITH THIS KINDERGARDEN TIER PROBLEM.

>> No.8289868

>>8289858
>KINDERGARDEN

you either need to know calculus or use the disassemble acceleration in the third standard formula

>> No.8289880

>>8289868
You don't need to know calculus to find the area of a triangle.

>> No.8289883

>>8289880
you need it to know that the integral of velocity is acceleration, and that the area under a curve is the integral

>> No.8289890

>>8289883
Doesn't matter, this "level" of calculus is for 15yo kids.

>> No.8289894

>>8289883
>linear function
>curve

what did he mean by this?

>> No.8289896

>>8289753
That post at >>8289186 was asking whether to assume linear deceleration, not specifying it.

>> No.8289899

>>8289858
nice job spelling kindergarten wrong

>> No.8289902

>>8289883
>the integral of velocity is acceleration
Forgot to mention, this proved my point
>kindergarden thread

>> No.8289903

>>8289899
Fuck spelling in foreign languages

>> No.8289916

this question is too hard
is it 100 seconds?
what is acceleration anyway if not a figment of our imagination

acceleration doesnt exist except in our minds