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Homework Help: What is the gravitational potential energy of the obectj

  1. Oct 22, 2007 #1
    hi, please help me figure these problems out. much appreciated.

    1. an object of mass .7kg is thrown vertically upwards at a speed of 29 m/s. What is the gravitational potential energy of the obect at the highest point of its trajectory?

    2. an object of mass 8.9kg moves with initial speed 21 m/s then interacts with its environment, gaining 1.6J of energy. What is the speed of the object after after the interaction is completed?
  2. jcsd
  3. Oct 23, 2007 #2
    1. You have to consider the gravitational potential at the start point as zero. Then the potential at the highest point equals to the dynamic energy of the object or:

    E = 1/2mv^2.

    2. After the interaction, the dynamic energy is reduced by 1.6J. You can calculate the speed reduction via equ. deltaE=1/2m(deltav)^2. Then the final speed is known by a subtraction
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