
#1
May2910, 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 ? 



#2
May2910, 12:16 PM

Sci Advisor
HW Helper
Thanks
P: 26,167

Hi rsoy!
(btw, it's how (rhyming with now and Mao) not who (rhyming with new and you) ) 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. 



#3
May3010, 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 



#4
May3010, 05:37 AM

Sci Advisor
HW Helper
Thanks
P: 26,167

who I can find the displacement in this Q ?
(try using the X^{2} tag just above the Reply box )
Yes, that's fine (except 180 + 202.5 = 382.5 ) 



#5
May3010, 01:54 PM

P: 14

Hmm not sure what you guys are talking about..but il get it later.



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