AP Physics 1 Question 215: Answer and Explanation

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Question: 215

5. A block of mass 3.5 kg slides down a frictionless inclined plane of length 6.4 m that makes an angle of 30° with the horizontal. If the block is released from rest at the top of the incline, what is its speed at the bottom?

  • A. 5.0 m/s
  • B. 6.4 m/s
  • C. 8.0 m/s
  • D. 10 m/s

Correct Answer: C



The only force doing work on the block as it slides down the inclined plane is the force of gravity, so the Work-Energy Theorem can be applied with the total work equal to the work done by gravity. The work done by gravity as the block slides down the inclined plane is equal to the negative change in potential energy.