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 one year ago
A 2m wide car is moving uniformly with a speed of 8m/s along the edge of a straight horizontal road. A pedestriun starts to cross a road with a speed "v" when the car is 12 m away from him. The minimum value of v for the pedestrian to cross the road safety is ?
 one year ago
A 2m wide car is moving uniformly with a speed of 8m/s along the edge of a straight horizontal road. A pedestriun starts to cross a road with a speed "v" when the car is 12 m away from him. The minimum value of v for the pedestrian to cross the road safety is ?

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ash2326
 one year ago
Best ResponseYou've already chosen the best response.0There can be two cases, either the man crosses the road before the car reach him or he crosses it after the car has crossed

mathslover
 one year ago
Best ResponseYou've already chosen the best response.0well if we take the man to reach more safely there is that is the first case

ash2326
 one year ago
Best ResponseYou've already chosen the best response.0see the diagramdw:1361020408653:dw Time taken for car to reach the man, \[12 m\div 8 m/s= 1.5 seconds\] In this time the man should cover the 2 meter distance, fairly simple now Can you find v?

DLS
 one year ago
Best ResponseYou've already chosen the best response.1dw:1361020539994:dw @ash2326 just trying..i dont think there will be 2 cases,he should move making an angle theta with the axis not straight..

mathslover
 one year ago
Best ResponseYou've already chosen the best response.0yeah @DLS has a point\

ash2326
 one year ago
Best ResponseYou've already chosen the best response.0But we need to find the minimum V for that, he has to walk straight

mathslover
 one year ago
Best ResponseYou've already chosen the best response.0the man will make an angle theta first we have to find the componenets ( x and y ) and then solve for theta

ash2326
 one year ago
Best ResponseYou've already chosen the best response.0dw:1361020702285:dw We aren't given D, we can't find angle without it

mathslover
 one year ago
Best ResponseYou've already chosen the best response.0dw:1361020857966:dw

DLS
 one year ago
Best ResponseYou've already chosen the best response.1\[v=\frac{d}{t} \] \[BC=2cosec \theta\] \[t_{bus}=t_{boy} \] \[\frac{4+2\cot \theta}{8}=\frac{8}{v}=2\sin \theta+\cos \theta \] \[v=\frac{8}{2\sin \theta+\cos \theta}\] for v to be minimummmmmmmmmmm \[\frac{dv}{d \theta}=0\] \[\frac{d8(2 \sin \theta+\cos \theta)^1}{d \theta}=0\]

DLS
 one year ago
Best ResponseYou've already chosen the best response.1sorry i took the distance 4m correct that value..

DLS
 one year ago
Best ResponseYou've already chosen the best response.1if my solution is close enough

mathslover
 one year ago
Best ResponseYou've already chosen the best response.0how r those angles : 2 cot theta and 2 cosec theta ?

DLS
 one year ago
Best ResponseYou've already chosen the best response.1\[\LARGE \frac{12+2\cot \theta}{8}=\frac{8}{v}=\frac{6+\cot \theta}{4}\]

ash2326
 one year ago
Best ResponseYou've already chosen the best response.0How do you have 8/v? man isn't travelling 8 meters

DLS
 one year ago
Best ResponseYou've already chosen the best response.1@ash2326 I equated the times.. Tbus=Tboy

ash2326
 one year ago
Best ResponseYou've already chosen the best response.0I know that but man has to travel \[\sqrt{2^2+(2\cot \theta)^2}\] so it should be \[\frac{\sqrt{2^2+(2\cot \theta)^2}}{v}\]

DLS
 one year ago
Best ResponseYou've already chosen the best response.1yeah i got ur query,hold on

DLS
 one year ago
Best ResponseYou've already chosen the best response.1i took that 12+2cot theta that is the total distance he has to travel i guess distance is scalar :o so why are u adding it vectorally? im getting confused too :S

ash2326
 one year ago
Best ResponseYou've already chosen the best response.0I solved this, there is no global minima for v. We need to revisit the problem

mathslover
 one year ago
Best ResponseYou've already chosen the best response.0got to go now,,,... sorry but please post your opinions

ash2326
 one year ago
Best ResponseYou've already chosen the best response.0@DLS the man is travelling with an angle, his speed is v I just found the hypotenuse distance

DLS
 one year ago
Best ResponseYou've already chosen the best response.1i thought that was 2 cosec theta :O

ash2326
 one year ago
Best ResponseYou've already chosen the best response.0Yes, if you solve the square root, you will get 2 cosec theta

ash2326
 one year ago
Best ResponseYou've already chosen the best response.0I'm not convinced about the car travelling an extra distance 2 cot theta

ash2326
 one year ago
Best ResponseYou've already chosen the best response.0@mathslover do you have answer for this?

DLS
 one year ago
Best ResponseYou've already chosen the best response.1Just do the whole thing for him :P From the beginning :D

mathslover
 one year ago
Best ResponseYou've already chosen the best response.0yep  4/3  ans..

Mashy
 one year ago
Best ResponseYou've already chosen the best response.0doing all that other crap!! :P.. good thing you put up the answer!!

mathslover
 one year ago
Best ResponseYou've already chosen the best response.0@Mashy you cn put up your soln... I posted it becz ash wnted to check the ans... Please post your soln

Mashy
 one year ago
Best ResponseYou've already chosen the best response.04/3 is the simple method.. of going straight :O..

DLBlast
 one year ago
Best ResponseYou've already chosen the best response.0before i can start i need to know the in physics what is the start point for all formula is = to ? or 0.00 or what the name of all start point plz? start point =

ash2326
 one year ago
Best ResponseYou've already chosen the best response.0@mathslover Use my first post, I had told you for minimum it has to be straight

mathslover
 one year ago
Best ResponseYou've already chosen the best response.0DLS can you tell me how you got 2 cot theta there ?

mathslover
 one year ago
Best ResponseYou've already chosen the best response.0dw:1361184323999:dw ok :)

DLS
 one year ago
Best ResponseYou've already chosen the best response.1isnt the sol clear? they are taking for it to be going straight

mathslover
 one year ago
Best ResponseYou've already chosen the best response.0But I am trying to do for the angle theta... please tell how you got 2 cot theta there

DLS
 one year ago
Best ResponseYou've already chosen the best response.1wait I got confused :P sec

DLS
 one year ago
Best ResponseYou've already chosen the best response.1dw:1361185375230:dw AC=2 cot theta

DLS
 one year ago
Best ResponseYou've already chosen the best response.1\[\LARGE \cot \theta=\frac{1}{\tan \theta}\]

DLS
 one year ago
Best ResponseYou've already chosen the best response.1\[\LARGE \cot \theta=\frac{AC}{2}\]

mathslover
 one year ago
Best ResponseYou've already chosen the best response.0OH got it thanks a lot
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