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Help with some forces questions

  1. Oct 8, 2006 #1
    Hey everyone, can someone check a few of my homework questions for me? I got most of them right...having trouble with these six questions though. Thanks!

    -------------------------

    1. The same horizontal force is applied to objects of different mass. The resulting acceleration is measured for each object. Which of the following graphs correctly represents the experimental results? Assume that in each case the horizontal force is the only force acting on the objects.

    link to image: http://img208.imageshack.us/img208/5512/quest1kx5.jpg

    My Answer: C

    3. The values of the masses attached to an Atwood machine are listed below. For which case is the acceleration the largest in magnitude?

    a. m1 = 200 grams, m2= 400 grams
    b. m1 = 300 grams, m2= 300 grams
    c. m1 = 100 grams, m2= 500 grams
    d. m1 = 200 grams, m2= 400 grams
    e. m1 = 150 grams, m2= 450 grams

    My Answer: D

    6. The values of the masses attached to an Atwood machine are listed below. For which case is the acceleration the largest in magnitude?

    a. m1 = 200 grams, m2= 400 grams
    b. m1 = 300 grams, m2= 500 grams
    c. m1 = 100 grams, m2= 300 grams
    d. m1 = 1200 grams, m2= 1400 grams
    e. m1 = 750 grams, m2= 550 grams

    My Answer: E

    7. The figure below shows the free-body diagram for a box as it is being dragged along a rough horizontal surface at a constant velocity. The background grid provides a scale for the magnitude of the forces. The normal force is not shown in the figure. Based on the scale provided what should be the magnitude of the normal force?

    link to image:
    http://img504.imageshack.us/img504/5281/forcediagramnx4.png


    a. 100 N
    b. 200 N
    c. 300 N
    d. 400 N
    e. More information is needed to answer the question

    My Answer: C

    9. On a frictionless surface on earth you need to apply a force F to accelerate a heavy box. If you had to do the same thing on the moon (frictionless surface also) and obtain the same acceleration, you would need

    a. much less force
    b. much more force
    c. the same force

    My Answer: B

    13. The figure below shows the free-body diagram for a box as it is being dragged along a rough horizontal surface. The background grid provides a scale for the magnitude of the forces. The normal force is not shown in the figure. Based on this diagram what is the acceleration of the box? Use g = 10 m/s2

    link to image:
    http://img61.imageshack.us/img61/1492/forcediagram2ss2.png

    a. 10 m/s2
    b. 5 m/s2
    c. 1 m/s2
    d. 0
    e. More information is needed to answer the question

    My Answer: A
     
  2. jcsd
  3. Oct 8, 2006 #2

    Andrew Mason

    User Avatar
    Science Advisor
    Homework Helper

    For 1. the image link does not work.

    Why? Explain your answer. d. is the same as a. so there must be a mistake. What is the magnitude of the acceleration in terms of the two masses?

    Why? Explain your answer.

    Again, why? What is the vertical component of the tension? How does it affect the normal force?

    You seem to be guessing. Explain your reasoning.

    Now I know you are just guessing. Explain first and we will try help.

    AM
     
  4. Oct 8, 2006 #3
    opps, sorry

    Hey AM --

    I had actually written my answers down for two seperate homework assignments (we do them on the Internet) and saved them in two different notepads. I actually posted the answers to the other homework assignment (was in a hurry when doing this - had to leave for the library with friends). Lol, it does seem like I was guessing on those when I looked it over...I feel foolish now.

    Here is what I meant to post, sorry!! I really need to print these out and circle the letters after doing the work, rather than doing the work and keeping just the letter answers in notepad. This even confused me and I'm in front of it now! Again, sorry.


    1. A
    3. C
    6. C
    7. A
    9. C
    13. D
     
  5. Oct 8, 2006 #4

    Andrew Mason

    User Avatar
    Science Advisor
    Homework Helper

    You had me worried there.

    I can't check 1. but the others are right.

    AM
     
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