Physics Help Forum Calculating braking distance

 Kinematics and Dynamics Kinematics and Dynamics Physics Help Forum

 Sep 30th 2018, 01:12 AM #1 Junior Member   Join Date: Sep 2018 Posts: 2 Calculating braking distance So I need to calculate the braking distance Relevant factors (deceleration of 5gs for a duration of 0.35seconds) Speed = 1000km/hour With this how can I calculate the distance it will take to brake?
 Sep 30th 2018, 03:20 AM #2 Senior Member   Join Date: Aug 2010 Posts: 415 First calculate the time required. At constant deceleration -5g= -49 m/s^2, your speed will go from 1000 km/s= 1000000 m/s to 0 in 1000000/49= 20408 s. During that time you will have gone a distance of (49/2)(20408)^2= 10204081633 m= 10204081.633 km.
Sep 30th 2018, 04:58 AM   #3
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Join Date: Apr 2017
Posts: 493
 Originally Posted by HallsofIvy First calculate the time required. At constant deceleration -5g= -49 m/s^2, your speed will go from 1000 km/s= 1000000 m/s to 0 in 1000000/49= 20408 s. During that time you will have gone a distance of (49/2)(20408)^2= 10204081633 m= 10204081.633 km.
That's some car Ivy !! a million meters a second is 2 Million MPH

Initial speed 1000 Km per 3600 secs = 277m/sec ....deceleration 49m/s2 brakes applied only for 0.35sec v=u + ft2

v = 277- 49x .35 x .35 ..................271m/sec this is the speed after breaking

You want to know "the distance it will take to brake" ... the car will still be moving after this ....

Average velocity during breaking is 274m/sec ...in 0.35 sec it will travel 96 meters

Distance travelled during breaking is 96 meters

Last edited by oz93666; Sep 30th 2018 at 05:38 AM.

 Sep 30th 2018, 10:33 AM #4 Junior Member   Join Date: Sep 2018 Posts: 2 What about this approach? Using s = vt +1/2at^2 v = 277.778 ms (1000km/hr -> m/s) a = 5*9.81 t = v/a (277.778/5*9.81) =5.6632 so s = 2359meters
Sep 30th 2018, 09:34 PM   #5
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Join Date: Apr 2017
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 Originally Posted by bcornelis Using s = vt +1/2at^2 v = 277.778 ms (1000km/hr -> m/s) a = 5*9.81 t = v/a (277.778/5*9.81) =5.6632 so s = 2359meters
Error in line 4

You have already specified breaks were applied for 0.35 secs ...

How far will it travel in 0.35 secs when max speed is 277 ???

 Tags braking, calculating, distance

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