who I can find the displacement in this Q ?


by r-soy
Tags: displacement
r-soy
r-soy is offline
#1
May29-10, 11:09 AM
P: 159
Hi all



who I can find the displacement in this Q ?



A jetliner lands with a speed of 90 m/s on runway . It runs with constant speed for 2 s , before the brakes are applied . The brakes produce a deceleration of 20 m/s2 . What is its displacement on the runway .



I try to solve



V0 = 90 m/s

t1 = 2s

x = V0 X t1 = 180 m

a = -20 m/s2



then I don't know who I complte it ?
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tiny-tim
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#2
May29-10, 12:16 PM
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Hi r-soy!

(btw, it's how (rhyming with now and Mao) not who (rhyming with new and you) )
Quote Quote by r-soy View Post
A jetliner lands with a speed of 90 m/s on runway . It runs with constant speed for 2 s , before the brakes are applied . The brakes produce a deceleration of 20 m/s2 . What is its displacement on the runway .
This is how

The total displacement is the sum of the two displacements.

Your first displacement is ok.

For the second displacement, use one of the standard constant acceleration equations, with distance = s, acceleration = a = -20, u = 90, and v = 0.
r-soy
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#3
May30-10, 05:21 AM
P: 159
see

Here I must find two displacement .
firist one I got it
now the secound now

I have Dx1 = 180 and a = -20, u = 90, and

by equat5ion constant I use v^2 = v0^2 = 2aDx
fainal velocity is 0 beacuse it will stop after using brake
now :
0 = 90^2 + 2(-20) Dx2
Dx2 = 202.5

Now collect two dispkacement : will get : 362.5 m

tiny-tim
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#4
May30-10, 05:37 AM
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who I can find the displacement in this Q ?


(try using the X2 tag just above the Reply box )

Yes, that's fine

(except 180 + 202.5 = 382.5 )
TwigLaser
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#5
May30-10, 01:54 PM
P: 14
Hmm not sure what you guys are talking about..but il get it later.


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