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Homework Help: Planets, Meteors, and booster rockets space

  1. Jan 1, 2013 #1
    1. The problem statement, all variables and given/known data
    An asteroid 5 km in diameter and mass 3.3x10^14 kg had been discovered moving towards earth at a speed of 20km/s and is 4 months away from direct contact. Lukily there are booster rockets parked in space and in a day or so one can be attached to the asteroid. What cpntinuous sideways thrust must be applied to make it just miss the earth of radius 6400 km . Ignore the grav. force of earth. Answer in N.

    2. Relevant equations
    3. The attempt at a solution

    I have no idea how to do this question..It'd be great if u can get me started and help me through this question. Thanks alot.
  2. jcsd
  3. Jan 1, 2013 #2


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    You wish to move the asteroid at right angles to its curent motion. How far do you wish to move it in that direction, and how long do you have to do it in? What equations do you know relating distance, time and uniform acceleration?
  4. Jan 1, 2013 #3
    okay so u need to move it so it just missses earth 1km i guess.. and the time to do this is approximately 4 months.
    but how would i find the amount of force
  5. Jan 1, 2013 #4


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    Since the constant thrust is applied continuously, it's just a constant acceleration problem (for the sideways motion...you can just ignore the towards Earth motion). For all of these problems, just list your givens and unknowns.


    d = 6400 km + x

    where "x" is some value required to clear the Earth. You have to take into account the non-zero size of the asteroid when deciding what x should be.

    vi = 0 km/s (initially no sideways motion)

    t = 4 months - 1 day


    a = ?

    Can you think of a kinematics equation that will allow you to solve your unknowns given your knowns?

    Once you have the acceleration, you can find the force, right?
  6. Jan 1, 2013 #5
    yes thanks a lot sir...i got the solution :) have a good day
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