AP Physics 1 Question 37: Answer and Explanation

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Question: 37

7. A projectile of mass m is fired into the air at some angle θ. If its launch velocity is v0, which of the following expressions represents the object’s kinetic energy at the peak of its motion?

  • A. 0
  • B. (1/2)m(v0 sin θ)2
  • C. (1/2)m(v0 cos θ)2
  • D. (1/2)m[(v0 sin θ)2 + (v0 cos θ)2 ]

Correct Answer: C


C At the peak of its motion, the object is only moving horizontally. Furthermore, because there is no horizontal acceleration, its horizontal velocity will be the same at the peak as it is at the launch. Finally, remember that cos θ (not sin θ) is used for taking the horizontal component.