Fig. 1 shows a hydraulic lifting platform used by a bicycle repair shop. A student pushes down on the small piston with a force of 180 N. The liquid in the ...
Question 1 Report
Fig. 1 shows a hydraulic lifting platform used by a bicycle repair shop. A student pushes down on the small piston with a force of 180 N. The liquid in the connected cylinders is oil. The pressure is transmitted through the liquid to the larger piston, which raises a bicycle.
(a) Calculate the pressure produced in the oil by the small piston. Give the unit. [2]
(b) State the name of the principle that allows pressure to be transmitted through a confined liquid. [1]
(c) Calculate the upward force on the large piston. [3]
(d) Explain why the force on the bicycle can be much greater than the force applied by the student. [3]
Answer Details
(a) Pressure is force per unit area:
\[p=\frac{F}{A}=\frac{180\text{ N}}{0.0040\text{ m}^2}=45000\text{ Pa}\]
[2]
(b) This transmission of pressure through a confined liquid is Pascal's principle, also called Pascal's law. [1]
(c) The pressure in the oil is \(45000\text{ Pa}\). Apply \(F=pA\) to the large piston:
\[F=45000\text{ Pa}\times0.120\text{ m}^2=5400\text{ N}\]
[3]
(d) Pressure is transmitted equally throughout the enclosed oil. The large piston has a much greater area than the small piston, and \(F=pA\). The same pressure acting over the larger area therefore produces a greater upward force on the bicycle. [3]
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