Suzie (of mass 98 kg) is roller-blading down
the sidewalk going 40 miles per hour. She
notices a group of workers down the walkway
who have unexpectedly blocked her path, and
she makes a quick stop in 1.1 seconds.
What is Suzie's average acceleration?
Answer in units of m/s^2. Also, what force was exerted to stop her, and where did this force come from?
Okay, so for the first part I subtracted 40 from 0 (for initial and final velocity) and got -40. Then I divided by 2 to get 20. I divided it all by 1.1 and got an answer, but that answer is in mph/s. How do I convert it? Is that how I'm supposed to do it?
Then for the force I multiplied 98 by my answer for acceleration. I got an answer, but I know it's wrong because I didn't convert the last answer.
As far as the force that is stoping her, isn't it a combination of the friction of rollerskates, gravity, the friction of her against air, and the ground pushing up?
2007-02-16 00:27:27 · 4 answers · asked by Nikita R 2 in Science & Mathematics ➔ Physics
Thanks for the people who are trying to help.
To all others, I am not trying to get an answer. I need help to understand the concepts because I do not have a textbook. As far as this noe being homework solutions, dear, I beleieve that another word for answer is solution, but besides your obvious lack of a definitive vocabulary, I suggest you spend more time preaching to your family and off the computer. Atleast I have an excuse.
2007-02-16 00:51:34 · update #1
didn't you already ask this?
2007-02-16 00:37:04 · answer #1 · answered by dreamoutloud2 3 · 0⤊ 0⤋
Dear, some questions for you. Yes, this is supposed to be answers, but it is NOT supposed to be homework solutions.
What is acceleration? Don't give me mathematics formulas but answer it in terms of words. Now, using your definition think about reworking your solution.
Now, for the later question and this one you can get mathematical on us. Newton gave us a formula that relates three things: F(orce), M(***) and A(cceleration). What is that formula?
After you work through the first part of your question you have enough to answer the last.
The very last part. Remember, force is a vector it has a size as well as a direction. I assume the problem is asking what stopped her motion towards the workers and not what is stopping her motion towards the center of the earth.
Update:
If you bother to read through the whole post I take you through the solution, but I do not give it to you.
Update II:
Asking the question in the first place is fine, I have no problem with that. However, I knew there would be people solving your problem for you and that is what I object to.
2007-02-16 08:44:39 · answer #2 · answered by MAF 2 · 0⤊ 0⤋
Use 1 mph = 1.6093 km
Hence 40 mph = 40 x 1.6093 kmph
Next u need to convert km/h to m/s
Hence 40 mph = 40x1.6093x(5/18) = v (say)
Then calculate avg accn a = (v-0)/1.1
force = 98xa
Ur mistakes,
u didnt convert mph to m/s
u dont need to divide by 2 (I wonder why u did that)
regarding stopping force ur correct
2007-02-16 08:42:23 · answer #3 · answered by GemX 2 · 0⤊ 0⤋
Wow, Suzie is huge.
2007-02-16 08:30:17 · answer #4 · answered by angrysandwichguy_2007 4 · 0⤊ 0⤋