1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Basic Physics Question-But I'm stuck!

  1. Jan 24, 2014 #1
    So as I have been completing my physics homework, there is one question I can not get passed. However I feel as if I already have the answer. The question is: What is the speed of the car 10.0 s after it begins its motion if it continues to move with the same acceleration?

    The original problem states that:A certain automobile manufacturer claims that its deluxe sports car will accelerate from rest to a speed of 44.5 m/s in 8.90 s.

    From what I have worked out the answer is 22.5m/s but it keeps telling me I am wrong. Any help would be greatly appreciated. Thank you!

  2. jcsd
  3. Jan 24, 2014 #2
    Well, without giving it all away, do you think that is a reasonable answer? (As you have stated the question, it is not.)
  4. Jan 24, 2014 #3
    I think it would be helpful if we could see the work you've done, that way we can identify where exactly the mistake is!
  5. Jan 24, 2014 #4
    So I went ahead and found the distance by multiplying (1/2)*44.5*10 which came out as 225. I then divided that by 10 which is the time interval the question wants me to identify. I get 22.5 which is obviously wrong for some reason, but I am still stuck nonetheless.
  6. Jan 24, 2014 #5
    Your numbers are slightly off (even for what you are doing), but my main objection is this: the question tells you that the car accelerates from rest with the same acceleration all the time - yet you claim that it will travel slower after 10 seconds than it did after 8.9 seconds.
  7. Jan 25, 2014 #6
    No…at 8.9 seconds it is traveling at the same speed.
  8. Jan 25, 2014 #7
    Maybe I am reading this completely wrong then? "A certain automobile manufacturer claims that its deluxe sports car will accelerate from rest to a speed of 44.5 m/s in 8.90 s." To me, that certainly sounds like the car travels at 0 m/s in the beginning, and at 44.5 m/s after 8.90 s.
  9. Jan 25, 2014 #8
    Uh, I'm sorry, I really don't know what I am doing with this problem. I keep getting confused with its acceleration and speed. Could you point me in the direction you would go for this problem?
  10. Jan 25, 2014 #9
    Okay nevermind, it was just 5*10.
  11. Jan 25, 2014 #10
    And you understand right, correct? The average acceleration of the car is ##5 \frac{m}{s^2}##, and multiplying that by the time given (ten seconds) gives you the velocity at that time.
  12. Jan 25, 2014 #11
    Got it. Thanks.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted