MCAT Physics Question 50: Answer and Explanation

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Question: 50

5. A hydraulic lever is used to lift a heavy hospital bed, requiring an amount of work W. When the same bed with a patient is lifted, the work required is doubled. How can the cross-sectional area of the platform on which the bed is lifted be changed so that the pressure on the hydraulic lever remains constant?

  • A. The cross-sectional area must be doubled.
  • B. The cross-sectional area must be halved.
  • C. The cross-sectional area must be divided by four.
  • D. The cross-sectional area must remain constant.

Correct Answer: A

Explanation:

This question tests our understanding of Pascal's principle, which states that a change in pressure applied to an enclosed fluid is transmitted undiminished to every portion of the fluid and to the walls of the containing vessel. We are told that the work required to lift the bed with the patient is double the work needed to lift just the bed. In other words, the force required doubles when both the bed and the patient have to be lifted. To maintain the same pressure, we must double the cross-sectional area of the platform of the hydraulic lever on which the patient and the bed are lifted.

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