AP Physics 1 Question 305: Answer and Explanation

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Question: 305

3. Escape velocity is defined as the minimum speed at which an object must be launched to "break free" from a massive body's gravitational pull. Which of the following principles could be used to derive this speed for a given planet?

  • A. Conservation of Linear Momentum
  • B. Newton's Third Law
  • C. Conservation of Angular Momentum
  • D. Conservation of Energy

Correct Answer: D

Explanation:

D

If an object leaves a planet at exactly escape velocity, its speed will approach zero as its distance from the planet approaches infinity. Zero speed implies zero KE, and infinite separation implies zero Ug if our reference separation is infinity. Thus, the total mechanical energy of an object traveling at escape velocity is 0 J. That's why conservation of energy is the relevant concept.