1.8. Pressure
A subsection of Physics, 5054, through 1. Motion, forces and energy
Listing 10 of 156 questions
A U-shaped tube, of constant cross-sectional area, contains some water of density 1000 kg / m3. Oil that does not mix with water is then poured into the right-hand side of the tube. shows the levels of the water and the oil when equilibrium is reached. 0.066 m X Y oil 0.075 m water Points X and Y are at the same horizontal level. X is 0.066 m below the top surface of the water. Y is 0.075 m below the top surface of the oil. State two quantities that influence the pressure beneath the surface of a liquid. 1. 2. The cross-sectional area of the tube is 5.0 × 10–4 m2. Calculate the mass of water above the level of X. mass = The pressure caused by 0.066 m of water at X is equal to that caused by 0.075 m of the oil at Y. Determine the density of the oil. density =
5054_w10_qp_22
THEORY
2010
Paper 2, Variant 2
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shows a can of compressed air that is being used to blow dust off a computer keyboard. The pressure of the air inside the can is greater than the pressure of the atmosphere. State what is meant by the term pressure. Explain, in terms of molecules, why the pressure of the air inside the can decreases as it is used. A student uses an inverted measuring cylinder in a water trough to measure the volume that the air occupies at atmospheric pressure. shows the equipment. measuring cylinder water rubber tubing air can (not to scale) Initially the inverted measuring cylinder is full of water. The student presses the top of the can and air passes through the rubber tubing into the inverted measuring cylinder. The air gradually replaces the water in the cylinder until no more air can leave the can. The final temperature of the air is equal to its initial temperature. The volume of the air inside the can is 1.8 × 10−4 m3. The student observes that, at an atmospheric pressure of 1.0 × 105 Pa, the total volume of the air in the measuring cylinder, the can and the tubing is now 9.4 × 10−4 m3. Determine the original pressure of the air in the can. pressure =
5054_w17_qp_21
THEORY
2017
Paper 2, Variant 1
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The density of water in a lake is 1000 kg / m3. At a depth of 25 m beneath the surface of the lake, the total pressure is 3.5 × 105 Pa. State what is meant by pressure. The gravitational field strength is 10 N / kg. Determine: the pressure due to 25 m of water pressure = the atmospheric pressure. atmospheric pressure = An underwater depth gauge contains a small cylinder as shown in . Gas is trapped inside the cylinder by a piston. The piston is free to move. outer face of piston piston gas The outer face of the piston is in contact with the water. As the depth gauge is lowered into the water, the piston moves into the cylinder. This moves a needle on a dial to indicate the depth of the gauge in the water. Explain why the piston moves into the cylinder. The temperature of the gas does not change as the piston moves into the cylinder. Explain, in terms of molecules, what happens to the pressure of the trapped gas as the piston moves into the cylinder. At the surface of the water, the volume of the trapped gas in the depth gauge is V0. On , sketch a graph to show how the volume of trapped gas decreases as the gauge is lowered into the water. V0 volume depth The instructions for the depth gauge state that, each time it is used, the needle of the dial must be re-set to zero at the surface of the water. Suggest one reason for this. The density of the air trapped in the depth gauge increases. The density of the water remains constant. Explain, in terms of the molecules of the water, why the density of the water remains constant.
5054_w20_qp_21
THEORY
2020
Paper 2, Variant 1
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Questions Discovered
156