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Problem on kinematics of body falling from space

  1. Jan 23, 2014 #1
    Problem goes like this.. body falls toward a planet with acceleration of
    -g0*R^2/s^2. where R is the radius of planet 4000 miles, g0 is 30 ft/s^2, s is the distance of the body from the planets center. the initial distance of the body from the surface is 400 miles. find the impact velocity.

    Pretty straight forward problem. i solved by substituting all the value in equation of acceleration and then finding impact velocity by equation v^2=u^2-2as. But the problem is i am getting the impat velocity as 6933 mph . The text book answer is different. Could someone please verify and let me know if i am right or wrong
    Would greatly appreciate the help.
    Thanks
     
  2. jcsd
  3. Jan 24, 2014 #2

    Simon Bridge

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    ... that equation only holds for constant acceleration - but the acceleration is not constant.
     
  4. Jan 24, 2014 #3
    yes just realised that.. thanks for the help.. used the varying acceleration equation and got the answer
     
  5. Jan 24, 2014 #4

    Simon Bridge

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    Sometimes your mind doesn't connect the dots until you tell someone else about it :)
    Well done.
     
  6. Jan 24, 2014 #5
    Ya happens more than often to me.. :) thanks anyways...
     
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