1. PF Contest - Win "Conquering the Physics GRE" book! Click Here to Enter
    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!

Two Rods

  1. Oct 17, 2009 #1
    1. The problem statement, all variables and given/known data
    Two uniform rods are connected to a table by pivots at one end. Rod B is longer than rod A. Both are released simultaneously from an initial angle θ. Neglect air friction. NOTATION: CM = center of mass; α = angular acceleration; |ay|= size of downward acceleration.

    1. αA and αB are dependent on θ.
    2. The density of the rods affect their rate of fall.
    3. |ax| of the CM initially equals 0 for both rods.
    4. αA and αB both increase with time.
    5. Rods A and B hit the table at the same time.
    6. αA and αB are the same initially.
    7. Just before landing, the CM of B has a greater speed than the CM of A.
    8. |ay| is initially equal for the CM of A and B.

    2. Relevant equations
    This is a multiple choice type of answer which one must choose from the following:

    -Stays the Same

    3. The attempt at a solution

    Well the first thing that threw me off was the "Decreases", "Increases", and "Stays the Same" answer because they do not even fit in the sentence.

    I was thinking that number (1) would be true because angular acceleration depends upon angular velocity which depends on theta (or an angle).

    Number (2), assuming that because there is no air resistance then the rods will have to be in a vacuum. Thus, density will have no effect.

    Number (3), not sure about this one.

    Number (4), angular acceleration does depend on time by the following formula: (change in angular velocity) / (change in time). Thus, the more time that is taken, the less the angular acceleration is. Thus, the answer would be false.

    And I am not sure about (5), (6), (7), or (8).

    Any help will be appreciated. Thanks.

  2. jcsd
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Can you offer guidance or do you also need help?
Draft saved Draft deleted