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Homework Help: Newton's Laws of Motion on a rocket

  1. Feb 6, 2009 #1
    Suppose the rocket is coming in for a vertical landing at the surface of the earth. The captain adjusts the engine thrust so that rocket slows down at the rate of 2.50m/s^2 . A 8.00-kg instrument is hanging by a vertical wire inside a space ship.

    1]Draw a free-body diagram for the instrument.

    2]Find the force that the wire exerts on the instrument.
  2. jcsd
  3. Feb 6, 2009 #2


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    Welcome to PF.

    I wonder why you didn't use the template that is provided when you make a new post... anyway, what did you come up with?
    What does your free body diagram look like? Which forces are acting on the block, in what directions and possibly magnitudes?
  4. Feb 6, 2009 #3
    w=mg acting on the instrument downwards. tension acting upwards. with a downward accelerating force.

    my attempted ans for qn 2 is mg - T = 2.5 * 8. gives the wrong tension result...

    can enlight me on where the mistake lies???
  5. Feb 6, 2009 #4


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    If the rocket is slowing, then the acceleration of the rocket is 2.5 upwards. This means that the Tension will be mg+2.5m = T = m*(g + 2.5)

    Even though the ship has downward velocity - in the direction of gravity - I read it that the speed is slowing at 2.5, hence this will create a force (m*a) in addition to gravity that will add to the force of gravity in the tension on the instrument won't it?
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