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Homework Help: Speed and Acceleration

  1. Oct 12, 2015 #1
    1. Luke's speed doubles. Does the size of his acceleration also double?

    2. No formulas or equations as this is a no-science physics course.

    3. If would say that Luke's acceleration doubles because to reach a higher speed you have to accelerate more.
  2. jcsd
  3. Oct 12, 2015 #2


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    Well, one way to approach such problems is to think about specific examples. In this case, let's say Luke is traveling along at an even 30mph. Later, after increasing his speed, he is traveling along at an even 60mph. What's the relationship between his acceleration in the two cases?
  4. Oct 12, 2015 #3


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    Have you stated your problem statement exactly as it was originally stated to you or is this a question you just want to ask? If it is a question put to you and you did not state it exactly as given, please restate exactly as originally given. If it your personal question simply say so.

    I am happy to help either way but if it is a problem given to you I want to make sure I understand it exactly.
  5. Oct 12, 2015 #4

    Hi and thank you very much for your reply!

    The question is exactly stated like this. The other two questions are even more confusing, especially the second one.

    I'll copy and paste it:

    "Please keep your answers neat and concise. These questions can be answered using two to four sentences and pictures as appropriate. After the due date, submit your work directly to your TA."

    1. Luke's speed doubles. Does the size of Luke's acceleration also double?

    2. A force is applied to an atom. What can be measured to determine the atom's mass? Explain your answer.

    3. In the video game Angry Birds, a bird collides with an initially vertical log. Why does the log only fall to the left or right?

    Again thank you so much, I made a terrible mistake choosing this course.
  6. Oct 12, 2015 #5


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    And do you have an answer to my question, or not?
  7. Oct 12, 2015 #6


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    1. When something is traveling at a constant speed there is no acceleration. Acceleration is only exists while increasing from one speed to another. From that statement what do you think the answer is?

    Have you already figured out the answers to 2. and 3?
  8. Oct 12, 2015 #7
    1. I think the answer is yes then because there is as significant increase in speed (times 2).

    2. I don't understand the question. As far as I know a spectrometer is used to determine an atom's mass.

    3. Angry Birds is a 2D game. Stuff that falls to the ground does to the left or right since there is no 360 degree view as it is in a 3D game.
  9. Oct 12, 2015 #8


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    1. I want you to look at my statement again and note that it states that a constant speed and an acceleration cannot exist at the same time. Stay with me and give this one more try.

    2. This same question has been ask in another thread and the only way I know how to answer it involves equations; and, the other thread states that there are no equations in this course.

    3. You have exactly the correct answer for this question.
  10. Oct 12, 2015 #9
    1. But you said "When something is traveling at a constant speed there is no acceleration. Acceleration only exists while increasing from one speed to another." Luke's speed doesn't stay the same because it doubles.
    Right now I'm kind of doubting that with the information provided a definite answer is possible. We were told that acceleration=change in object's velocity/change in object's time. The questions doesn't say anything about time.

    2. We have a minimum of equations we use such as the one I mentioned above. Another one the prof showed us is FG= GMm/R² (this being the "gravitational force between objects that have masses m and M").

    3. I hope you're right.
    Last edited: Oct 12, 2015
  11. Oct 12, 2015 #10


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    !. OK, you have been working on this so here we go.
    For example: The acceleration time to increase Duke's speed from 30 mph to 60 mph is exactly equal to the acceleration time to increase Duke's speed from 0 to 30 mph; so the total acceleration time from 0 mph to 60 is twice the time to accelerate him from 0 mph to 30. As a result, it might be stated that the "amount of Duke's acceleration time" has doubled; but to use the term "size of acceleration" is ambiguous and not really correct. The reason I asked you to restate the original question exactly as asked was that the term "size" seemed totally out of place in that statement.

    In the physics world, when the velocity of a mass is doubled what is also doubled is what is called its Kinetic Energy; so, in physics the correct statement is "When the velocity of Duke doubled, his Kinetic Energy is doubled".

    Sorry it has taken so long to end up giving you such an ubiquitous answer to your question; and, in the end, in spite of all of the above, saying the size has increased may actually be the answer your instructor is looking for.
  12. Oct 12, 2015 #11
    You have nothing to apologize for. I am extremely grateful! Thank you so much!
  13. Oct 12, 2015 #12


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    Suggestions for questions No. 1 and No. 3

    On No. 1
    First, ask your instructor if "size" means "rate".
    If the instructor's answer is: "Yes". Then your the correct answer to that question is "No".
    If the instructor's answer is "No"; then ask for clarification of the question, based upon: speed = acceleration rate x acceleration time

    ON No. 3
    This question is ambiguous as well because his acceleration does not double, "the acceleration rate stays the same and the time doubles" to accelerate from 0 to twice the lower speed.
    Ask if "more" means "for a longer time"

    Of course, by this time the instructor will probably realize you have been getting assistance from somewhere; and, maybe getting very annoyed as well. Good luck.
    Last edited: Oct 12, 2015
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