Anikate
  • Anikate
A driver in a car traveling at a speed of 75 km/h sees a cat 125 m away on the road. How long will it take for the car to accelerate uniformly to a stop in exactly 122 m? Answer in units of s.
Physics
  • Stacey Warren - Expert brainly.com
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SOLVED
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jamiebookeater
  • jamiebookeater
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Anikate
  • Anikate
any clue??
anonymous
  • anonymous
@pooja195 Help me
anonymous
  • anonymous
@pooja195 im new to helping

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More answers

Anikate
  • Anikate
do u know the answer??
Anikate
  • Anikate
@DylanisNOW u know the answer??
anonymous
  • anonymous
Im trying to get @pooja195
Anikate
  • Anikate
i thuink she offline, but do know the answer to this question??
Anikate
  • Anikate
she appeears to be offline??
Anikate
  • Anikate
yea she offline
anonymous
  • anonymous
Hold on...Im trying to figure it out. Please dont rush!
Anikate
  • Anikate
ok
anonymous
  • anonymous
@pooja195 No she isnt
Anikate
  • Anikate
ok, do u know how to do it though?
anonymous
  • anonymous
Give me a sec please
Anikate
  • Anikate
ok np
Anikate
  • Anikate
@pgpilot326 do u know how to do this? its a physics question
anonymous
  • anonymous
Think of the units.
Anikate
  • Anikate
ok now?
anonymous
  • anonymous
units are 75km/h right?
Anikate
  • Anikate
yes
anonymous
  • anonymous
Wait sorry hold on thats not it thats only 1
Anikate
  • Anikate
ok
anonymous
  • anonymous
75km/h / 125 m=?
Anikate
  • Anikate
600m/h
anonymous
  • anonymous
Okay do you have answer choices?
Anikate
  • Anikate
nopee
Anikate
  • Anikate
do u havea roungh estimate of what the andswer could be??
anonymous
  • anonymous
Think of it like this. Every second the speed decreases by?
anonymous
  • anonymous
We cant give answers...Its just help to get you to understand it!
anonymous
  • anonymous
Think of it like this. Every second the speed decreases by?
Anikate
  • Anikate
the speed decreases by seconds(squared)
anonymous
  • anonymous
Ok that is?
Anikate
  • Anikate
idk.....
anonymous
  • anonymous
.... @pgpilot326 can you help me help him?
anonymous
  • anonymous
Anyways..
Anikate
  • Anikate
dylanis, can u just post a step by step explaination for it
anonymous
  • anonymous
Ok
anonymous
  • anonymous
Step 1:units are 75km/h
anonymous
  • anonymous
Step 2:75km/h / 125=600m/h
anonymous
  • anonymous
Okay now we are at step 3
anonymous
  • anonymous
if a is a constant, integrate to get velocity and again to get position. the velocity should be linear and the position a quadratic.
anonymous
  • anonymous
since you know the initial and final speed you should be able to calc. the time
anonymous
  • anonymous
pgpilot should we make a equation?
anonymous
  • anonymous
should make 2 equations... velocity and position. you'll need both.
Anikate
  • Anikate
can you please show bothh?
Anikate
  • Anikate
and solve with steps please?
anonymous
  • anonymous
\[v \left( t \right)=v_0+at\]and\[x \left( t \right)=x_0+v_0t+\frac{ 1 }{ 2 }at^2\]
anonymous
  • anonymous
pg you are right good job btw :)
anonymous
  • anonymous
at t=0, initial speed (\(v_0\)) is 75 km/h and initial position is 0 m. at t=\(t_1\), final speed (\(v_f\)) is 0 km/h and final position is 122 m.
anonymous
  • anonymous
you need to solve for \(t_1\)
Anikate
  • Anikate
ok
Anikate
  • Anikate
how so??
Anikate
  • Anikate
which equation am i putting all this in??
anonymous
  • anonymous
phone, just a minute
anonymous
  • anonymous
\[v \left( t_1 \right)=0=75 +a\cdot t_1\] \[x \left( t_1 \right)=122=0+75t_1+\frac{ 1 }{ 2 }at_1^2\]
anonymous
  • anonymous
find roots of quadratic in terms of a.
Anikate
  • Anikate
u can handwrite it if u wish, ill prob be able to decode it
Anikate
  • Anikate
|dw:1443142704493:dw|
Anikate
  • Anikate
isnt htat what we have now?? what now??
Anikate
  • Anikate
can u show rest of steps
anonymous
  • anonymous
solve velocity eqn for t1 and position for t1 and equate
anonymous
  • anonymous
to solve for a. once you have a you can find t1
Anikate
  • Anikate
how do u solve for t1?? there are 2 variables in the equation itself
anonymous
  • anonymous
from velocity: t1 = -75/a
anonymous
  • anonymous
use quadratic to solve the position: \[0=-122+75t_1+\frac{ 1 }{ 2 }at_1^2\]for t1 in terms of a
Anikate
  • Anikate
|dw:1443143049231:dw|
Anikate
  • Anikate
|dw:1443143204081:dw| thats as far as i can get
Anikate
  • Anikate
can u please explain how u would do it, and go past that step
anonymous
  • anonymous
|dw:1443143218606:dw|
anonymous
  • anonymous
use the quadratic formula
anonymous
  • anonymous
|dw:1443143430909:dw|then solve for a
Anikate
  • Anikate
cant root a variable
Anikate
  • Anikate
keep going
anonymous
  • anonymous
you'll have to square to get rid of square root
Anikate
  • Anikate
ok then, can u plz post work till answer?
Anikate
  • Anikate
kinda hard to follow step by step
anonymous
  • anonymous
k but it will take a minute
Anikate
  • Anikate
take ur time
anonymous
  • anonymous
\[122=75\left( \frac{ -75 }{ a } \right)+\frac{ a\left( -75 \right)^2 }{ 2a^2} \Rightarrow 122 =-\frac{ 5625 }{ a } +\frac{ 5625 }{ 2a }\Rightarrow 244a = -11250+5625\]
anonymous
  • anonymous
\[a=-\frac{ 5625 }{244 } \Rightarrow t_1 = \frac{ -75 }{ -\frac{ 5625 }{ 244 } }=\frac{ 244 }{ 75} \text{ sec}\]
Anikate
  • Anikate
AAH ok! I see! thanks a lot! @pgpilot326

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