mass of container full of air = g mass of container with extra air = g volume of air released = cm 3

Size: px

Start display at page:

Download "mass of container full of air = g mass of container with extra air = g volume of air released = cm 3"

Frederick Nash
6 years ago
Views:

1 1992 Q32 The air pressure inside the passenger cabin of an airliner is 9 x 10 4 Pa when the airliner is at its cruising height. The pressure of the outside atmosphere at this height is 4 x 10 4 Pa. Calculate the resultant force on the cabin door, of area 3 m 2, caused by this difference in air pressure Q32 The apparatus in the diagram below may be used to measure the density of air. Using the foot pump, extra air. is pumped into the container. This extra air is released into the measuring cylinder as shown above and its volume measured. The following measurements, are recorded. mass of container full of air = g mass of container with extra air = g volume of air released = cm 3 What value do these results give for the density of air in kgm -3? 1994 Q33 Liquid nitrogen changes to its gaseous state at a temperature of -196 ºC What is this temperature in kelvin? Explain why a temperature of 0 kelvin is described as "the absolute zero of temperature".

2 1995 Q33 A skin diver carries her air supply in a steel cylinder on her back. She works at a depth where the pressure is 2.5 x 10 5 Pa. When full, the cylinder contains m 3 of air at a pressure of 1.6 x 10 7 Pa. Calculate the volume of air available to her at this depth from a full cylinder Q 32 Gas is often stored in cylinders at high pressure. The pressure of the gas must be reduced by a reduction valve before the gas can be used. The pressure of the gas in the cylinder is 20 x 10 5 Pa. The pressure of the gas as it leaves the reduction valve is 4 x 10 5 Pa. Gas with a volume of 0.01 m 3 enters the reduction valve from the cylinder. What is the volume of this gas when it leaves the reduction valve, assuming that the temperature of the gas does not change?

3 1991 Q4 The diagram below, taken from a physics textbook, shows the effect of increasing the force on a compression spring. This type of spring is used in the design of a safety device for a gas cylinder. The pressure of the gas in the cylinder is 5.0 x 10 5 Pa at a temperature of 20ºC. The area of the piston is 2.5 x 10-4 m 2. (i) What is the size of the force exerted by the gas on the piston? (ii) Explain how the device operates, if the gas pressure in the cylinder exceeds a safety limit. (c) The safety limit is set at a pressure of 9.0 x 10 5 Pa. At what temperature would this limit be reached by the gas described in part? Assume that any increase in volume of the gas in the cylinder can be neglected. The adjuster is screwed inwards. What would be the effect on the value of the pressure safety limit? Justify your answer.

4 1992 Q4 The apparatus shown below can be used as a type of thermometer. It consists of a bulb containing helium gas, the pressure of which can be monitored. The volume of the bulb is considered to be constant over the range of temperature measured by the thermometer. The following results for the temperature and pressure of the gas were obtained while calibrating the thermometer. (i) Copy the above table. Complete the table, giving the temperature in kelvin. (ii) Use the data from your completed table to establish the relationship between the pressure and temperature of the gas. (iii) Explain this change of pressure with temperature in terms of the movement of the helium molecules. When the bulb is immersed in a sample of liquid nitrogen, the meter gives a reading of 24 kpa for the pressure of the helium gas. Find the temperature of the liquid nitrogen sample.

5 1993 Q4 A pupil uses the apparatus below to investigate properties of a sample of gas. The volume of the sample of gas can be changed by moving the piston. The temperature of the sample of gas can be increased by using the heater. At the start, the pressure of the gas is 400 kpa and its volume is 1000 cm 3. During the investigation, the pressure and volume of the gas change as indicated by sections AB and BC on the graph below. During section AB, the temperature of the gas is constant at 300 K. (c) Calculate the volume of the gas when its pressure is 250 kpa during stage AB. State what happens to the pressure, volume and temperature of the gas over the section of the graph which starts at B and finishes at C. What is the temperature of the gas, in kelvin, corresponding to point C on the graph?

6 1994 Q3 A water rocket consists of a plastic bottle, partly filled with water. Air is pumped in through the water as shown in Figure 1. When the pressure inside the bottle is sufficiently high, water is forced out at the nozzle and the rocket accelerates vertically upwards as shown in Figure 2. (i) At take-off, the volume of air in the bottle is 750 cm 3 at a pressure of 1.76 x 10 5 Pa. Figure 3 shows the rocket at a later stage in its flight, when the volume of the air in the bottle has increased to 900 cm 3. Calculate the new pressure of the compressed air at this later stage In its flight. (ii) The area of the water surface which is in contact with the compressed air in the bottle is 5.0 x 10-3 m 2. Calculate the force exerted on the water by the compressed air at the new pressure. Explain fully why the rocket rises as the water is forced out at the nozzle.

7 1996 Q4 The diagram below illustrates an experiment to investigate the relationship between pressure and volume of a gas. The apparatus consists of a calibrated syringe fitted with a gas-tight piston. Air is trapped in the syringe and the pressure of the trapped air can be monitored using a pressure sensor and a meter. The pressure of the trapped air can be altered by exerting a force on the piston. The temperature of the trapped air is assumed to be constant during the experiment. The following measurements of pressure and volume are recorded. Using all the data, establish the relationship between the pressure and volume of the trapped air. The force on the piston is now altered until the volume of the trapped air is 5.0 cm 3. Calculate the pressure of the trapped air. (c) (d) The force is now removed from the piston. Explain the subsequent motion of the piston in terms of the movement of the air molecules. The tubing between the syringe and the pressure sensor is replaced by one of longer length. What effect would this have on the results of the experiment?

8 1997 Q4 A pupil uses the apparatus shown in the diagram to investigate the relationship between the pressure and the temperature of a fixed mass of gas at constant volume. The cylinder is fully immersed in a beaker of water and the water is slowly heated. You may assume that the volume of the cylinder does not change as the temperature of the water changes. Explain why the cylinder must be fully immersed in the beaker of water. The pressure of the gas in the cylinder is 100 kpa when the gas is at a temperature of 17 ºC. Calculate the pressure of the gas in the cylinder when the temperature of the gas is 75 ºC. (c) The base of the cylinder has an area of m 2. What is the force exerted by the gas on the base when the temperature of the gas is 75 ºC? (d) What happens to the density of the gas in the cylinder as the temperature increases from 17 ºC to 75 ºC? Justify your answer.

9 1998 Q4 The rigid container of a garden sprayer has a total volume of 8.0 litres (8 x 10-3 m 3 ). A gardener pours 5.0 litres (5 x 10-3 m 3 ) of water into the container. The pressure of the air inside the container is 1.01 x 10 5 Pa. Calculate the mass of air in the sprayer. [Data:- Density of air = 1.29 kgm -3 ]. The gardener now pumps air into the container until the pressure of the air inside it becomes 3.0 x 10 5 Pa. (i) The area of the water surface in contact with the compressed air is 7.0 x 10-3 m 2. Calculate the force which the compressed air exerts on the water. (ii) Water is now released through the nozzle. Calculate the final pressure of the air inside the sprayer when the volume of water falls from 5.0 litres (5 x 10-3 m 3 ) to 2.0 litres (2 x 10-3 m 3 ). Assume the temperature of the compressed air remains constant.

10 1999 Q4 Sketch a graph which shows how the pressure caused by a liquid depends on the depth below the surface of the liquid. Numerical values are not required but the axes should be clearly labelled. There is a buoyancy (upthrust) force on a submarine when it is submerged in sea water. (i) Explain fully how the buoyancy force is produced on the submarine. You may make reference to your graph from. (ii) The total volume of sea water displaced by the submarine is 14.5 m 3. Calculate the mass of sea water displaced by the submarine. [Data: Density of seawater = 1.02 x 103 kgm- 3.] (iii) The submarine changes depth by altering the mass of water stored in tanks in the submarine. Compressed air replaces some water in the tanks. Explain, in terms of the forces acting on the submarine, why replacing water in the tanks with compressed air causes the submarine to accelerate upwards.

11 2000 Q4 A toy diving bell consists of an inverted glass bulb, open at one end. The bulb contains a fixed mass of air trapped by water. The diving bell floats below the surface of the water in a sealed plastic bottle. The bottle is flexible and can be squeezed. The diving bell has a mass of 2.5 x 10-3 kg. Calculate the size of the upthrust (buoyancy force) acting on the bell when it is stationary. The trapped air inside the diving bell has a volume of 0.71 cm 3, and is at a pressure of 1.01 x 10 5 Pa. The bottle is now squeezed. This reduces the volume of air trapped inside the bell to 0.63 cm 3. The temperature of the trapped air remains constant. (i) Calculate the pressure of the trapped air after the bottle is squeezed. (ii) What happens to the volume of water inside the bell when the plastic bottle is squeezed? (iii) Explain why the diving bell sinks when the plastic bottle is squeezed Q4 A diver is a member of a marine archaeology team. The diver's air tank has an internal volume of 1.20 x 10-2 m 3. The pressure of the air in the tank is 2.50 x 10 7 Pa at 20 ºC. (i) Calculate the volume that the air in this tank would occupy at an atmospheric pressure of 1.01 x 10 5 Pa. Assume that the temperature remains constant. (ii) The density of air at a temperature of 20 ºC and at a pressure of 1.01 x 10 5 Pa is 1.20 kg m -3. Calculate the mass of the air in the tank.

FLOATING AND SINKING

NAME SCHOOL INDEX NUMBER DATE FLOATING AND SINKING 1. 1994 Q5a P2 (a) State Archimedes s principal (1 mark) 2. 1996 Q29 P1 A solid copper sphere will sink in water while a hollow copper sphere of the same