Pascal's Law And Hydraulics
In a hydraulic lift the small piston has an area of 5cm2 and the large piston an area of 250cm2. What downward force on the small piston is needed to support a car of weight 10000 N resting on the large piston?
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Solution
200 N
A hydraulic lift relies on Pascal's law, which states that a pressure applied to an enclosed incompressible fluid is transmitted undiminished to every part of the fluid and the container walls. Because the pressure is the same on both pistons, A1F1=A2F2, so a small force on the narrow piston balances a large force on the wide one. Solving for the input force, F1=F2A2A1=10000×2505=10000×501=200N. The value 100 N would require an area ratio of 1:100. The value 400 N doubles the correct force. The value 500 N uses an incorrect ratio of 1:20. This is the standard NCERT application of Pascal's law that explains the force-multiplying action of hydraulic machines. As a check, the area ratio of 50 means the device multiplies force fifty-fold, so lifting a 10000 N car with only 200 N input is exactly the expected mechanical advantage.
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About This Question
- Subject
- physics
- Chapter
- properties of solids and liquids
- Topic
- pascal's law and hydraulics
- Difficulty
- Easy
- Year
- 2025
Solution
Correct Answer:
200 N
A hydraulic lift relies on Pascal's law, which states that a pressure applied to an enclosed incompressible fluid is transmitted undiminished to every part of the fluid and the container walls. Because the pressure is the same on both pistons, A1F1=A2F2, so a small force on the narrow piston balances a large force on the wide one. Solving for the input force, F1=F2A2A1=10000×2505=10000×501=200N. The value 100 N would require an area ratio of 1:100. The value 400 N doubles the correct force. The value 500 N uses an incorrect ratio of 1:20. This is the standard NCERT application of Pascal's law that explains the force-multiplying action of hydraulic machines. As a check, the area ratio of 50 means the device multiplies force fifty-fold, so lifting a 10000 N car with only 200 N input is exactly the expected mechanical advantage.
This easy difficulty physics question is from the chapter properties of solids and liquids, covering the topic of pascal's law and hydraulics. It appeared in the 2025 exam.
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