# Physics

I really don't get why I am getting this question wrong? Please can you explain to me how to do this question step by step so that I can understand it please? :( i have been stuck on this question for quite a while now.

Determine the stopping distances for an automobile with an initial speed of 89 km/h and human reaction time of 2.0 s for the following:
(a) an acceleration a = -4.0 m/s2.
(b) a = -8.0 m/s2.

1. 👍 0
2. 👎 0
3. 👁 74
1. v=89 km/h=89000/3600= 24.7 m/s.
The distance covered during the reaction time is
s₁=v₀t₁=24.7•0.2=49.4 m
The distance covered during braking s₂
s₂=v₀t₂-at₂²/2
v=v₀-at₂
v=0 =>
t₂=v₀/a
s₂=v₀²/2a =24.7²/2•4=76.3 m
s=s₁+s₂ =49.4+76.3 =125.7 m

1. 👍 0
2. 👎 0
posted by Elena

## Similar Questions

1. ### Physics

I really don't get why I am getting this question wrong? Please can you explain to me how to do this question step by step so that I can understand it please? :( i have been stuck on this question for quite a while now. Determine

asked by Sarah on October 11, 2013
2. ### Physics

I really don't get why I am getting this question wrong? Please can you explain to me how to do this question step by step so that I can understand it please? :( i have been stuck on this question for quite a while now. Determine

asked by Sarah on October 11, 2013
3. ### Physics

I really don't get why I am getting this question wrong? Please can you explain to me how to do this question step by step so that I can understand it please? :( i have been stuck on this question for quite a while now. Determine

asked by Sarah on October 11, 2013

Actual question on homework."EXPLAIN HOW YOU CAN BREAK APART ARRAYS WHEN YOU MULTIPLY BY 3." (there is no array on the paper to use) I don't like this new math, what was wrong with the old math I learned, I am Accounting /Finance

asked by Jennfer on January 21, 2010
5. ### math,help

Can someone explain to me the reasoning involved in each step when simplifying the fraction 42/56. I had this question wrong in my previous exam...I don't know what i was thinking when answering it......but i like to know what was

asked by jas20 on March 4, 2007
6. ### Math :(

asked by I Dont Matter on March 13, 2018
7. ### Math

Consider the following test scores obtained by a class. Test score 90 80 70 60 50 Frequency 1 4 11 6 2 Find the standard deviation (rounded to the nearest hundredth). -------------------------------- I've posted this question

asked by Debin on December 4, 2012
8. ### ALGBRA

Consider the following test scores obtained by a class. Test score 90 80 70 60 50 Frequency 1 4 11 6 2 Find the standard deviation (rounded to the nearest hundredth). -------------------------------- I've posted this question

asked by Debin on December 4, 2012
9. ### math

hi i need to solve this question but i don't know how to do it when there is dividing included x(x-8):5=92 i did this much and then i found out that what i was doing was wrong x(x-8):5*5=92*5 2x-8=460 2x=468 x=234 but it seems

asked by louise on October 27, 2010
10. ### transformations

Hi I just got my correspondence back and the following question is wrong. Explain how the graph of f(x)=x^2-4x can be used to obtain the graph of y=g(x). Could you explain so I can see where I went so wrong. Thanks for your time.