Physics
Examination time] 1992
Js1. Doc
National physico-physics competition 1992
[content
National physico-physics competition 1992
I. Selected topics (42 points, 3 points each)
Only one of the answers listed below is correct. Fills the letters in brackets after the title before the correct answer。
1. 30 newton may be the gravity of which of the following objects?
A. One type of pupil. B. A car。
C. A pencil. A school bag full of textbooks。
2. During the summer, the refrigerator doors were opened and white fog was often seen. This is..
A. Pre-existing water vapour in refrigerators。
B. Water vapours that evaporate when the water in the refrigerator food is exposed to high temperature air。
C. Small crystals formed by water vapour cooling in air。
D. Small droplets formed from water vapour cooling in air。
3. When the incandescent light is broken, it also glows if it is reconnected. It's a time of power consumption compared to the original. Here
Growth。
B. Reductions。
C. No change。
D. Power consumption is higher or less than would otherwise be determined by the location of the light。
4. In order to measure more accurately the number of small rubber gaskets of similar specifications (estimated at 1,000), which of the following measures is best used
A. Collapse these gaskets together, measure the total thickness of l on a scale scale, and then a gasket
B. Collapse these gaskets together, measure the total thickness of l on a scale scale and measure 10 more mats
C. The total mass of these gaskets is measured in scales m, followed by a mass of m1,
The total mass of these gaskets is measured by the scales m and the mass of 10 more by mass m10。
5. Incandescent light bulbs are often spiraled in order to do so
A. To facilitate the spread of light threads and avoid their melting。
B. Minimize electrical resistance to lights。
C. Reduce the heat spread and increase the temperature of the light。
D. Reducing the rise in lighting at high temperatures。
6. Tractor tracks are made of a piece of metal with one or two bumps on each plate
A. The metal sheet and the elasticity above it are designed to reduce pressure on the ground。
B. The metal sheet and its elasticity are intended to increase pressure on the ground。
C. Metal sheeting is intended to reduce pressure on the ground; this is intended to increase pressure on the ground。
D. Metal sheeting is designed to increase pressure on the ground; it is implicit to reduce pressure on the ground。
7. In winter, tap pens are brought from the outside to the interior, sometimes with ink flowing out. It's important
A. The ink is swelled and flowing。
B. The ink was squeezed out by heat。
C. The air in the pocket is swelled by heat, and the ink is squeezed out。
D. The slits at the tip of the pen were heated, causing ink to leak。
8. The figure is a incandescent light bulb. The current at work is about..
A. 0. 27 millimetres. B. 270 millimetres。
C. 0. 41 amber. D. 0. 11 amber。
Ming cooked eggs twice. For the first time after the water has opened, the fire continues to boil until it is cooked; for the second time, the flames are reduced after the water has opened, but the water in the pot remains boiling until cooked. Twice
A. First measure is less time-consuming than second measure。
B. First measure is fuel-intensive but saves time。
C. Second measure saves fuel but takes time compared to the first measure。
D. The second measure saves fuel compared to the first measure, and the two measures take similar time。
A bicycle taillight is well designed. When the light in the back car reaches the taillight in any direction, it “reflects back”. The figure below shows the profile of the four taillights, in which the mirror mask used to reflect is of different shapes. This is the mirror that produces the effects
It's easy to get dust on the fibers because of it
A. Easy to accumulate static charge. B. Have some viscosity。
C. There are large pore. It's soft。
There's an arc gap on the tics of some electric meters, and there's a mirror underneath the gap, and it works
A. Keep the eyes in the right position when reading the numbers。
B. Growth of the brightness of the dial。
C. Checking the level of instrumentation。
D. Internal architecture for observational instruments。
People standing inside the car while the car was braked would be dumped forward. We need to use four words to explain this phenomenon
At one brake, the foot slowed down with the car
2 the movement of people and vehicles at similar speeds
The body of three persons is moving forward at the desired speed due to inertia
Four people will be dumped forward。
In which order does the four sentences follow to explain this phenomenon most clearly
A. 1234 b. 2134
C. 1324 d. 2314
14. In order to avoid damage to the scale, two small coppers of equal or similar mass on each package at both ends of the scale. The coppers at one end of the scale are now lost and the owner removes the coppers at the other end for fear of affecting the accuracy of the scales. That's what it's all about
A. The readings at the time of measurement are greater than the actual quality。
B. Less reading than actual quality when measured。
C. The accuracy of the scales can be restored regardless of whether the two coppers are identical in quality。
D. Capabilities restore the accuracy of the scales only when the two coppers are of exactly the same quality。
Ii. Filling in blanks (18 points, 3 points each)
When viewing the white area on the colour television screen with a magnifying glass, it is found to consist of bright spots or strips of colours。
2. The elucidation book of the spring puller states that it takes 10 newtons to stretch each spring by 10 centimetres. Wang has just stretched the pull in the chart by 0. 4 meters. Her pull is newton。
Thermal means of delivery used for cooking are important。
4. The distance between a person's vision and the visual watch at the time of examination shall be 5 metres. At present, because the house is too small to use a plane mirror, the distance between the visual watch and the mirror is 3 m (e. G. Graph), and the distance to the mirror is rice。
Doctors will gradually replace the old unit mm mercury column with an international unit of pa (l kpa = 1000 pascal) when measuring blood pressure. Mercury is known to have a density of 13. 6 x 103 kg/m3 and is known to be 1 pasco = newton/m3, which results in 1 mm mercury column = pascal. The principle of medical examination for admission to higher education institutions in 1991 states that candidates with an artery convulsion exceeding 11. 46 kpa cannot apply for such specialties as geological exploration, where 11. 46 kpa = mm mercury column。
There is a small light bulb marked “2. 5v0. 3a”. Lee hong calculated that its filamental resistance was 8. 3 om, but the result was 2. 5 om measured using the om watch (the instrument for measuring resistance). The most reasonable explanation for this difference is that electrical resistance to metals changes with 。
Iii. (4 minutes)
The following is a tectonic chart of a flashlight. There are two ways to connect. Press the button when the short time is used. Pushes the slide button forward over a long period of time。
Draw a circuit chart of this flashlight against a physical profile。
Iv. (6 minutes)
The construction of a toilet canal tank is shown as a figure (the device for pouring water into the tank is omitted). The rubber cap on the outlet is hollow, it floats on the surface and water flows from the outlet, as shown in figure (a). As the water flowed, the surface was reduced until the rubber cap covered the vent and the discharge process ended. During the inverted water and after filling the water, the rubber cap covers the vent, such as figure (b)。
1. Please judge how the gravity of the hollow rubber cap in figure (a) relates to the size of the floating power it receives。
2. Please explain why the rubber cover in figure (b) is so tight that it does not float。
3. An important flaw in such a device is that a tank of water is used every time a toilet is flushed. In order to save water, please make some changes to the rubber cap so that when you press the handle, the rubber cap lifts up and discharges the water, and when you release the handle, the rubber cap immediately covers the mouth and stops the discharge。
V. (6 minutes)
There is a hairdresser which, as a result of the loss of the elucidation book, only understands its rated volts to be 220 volts and has no other data. Draw a simple measure of the power of this blower, using the electric meters of the common household, the data on which are shown, and a clock。
Provides that:
1. Identification of the measurement chain;
2. The formula for the calculation of electrical power is exported by letters representing the amount of physics that is affected。
Vi. (8 minutes)
Hydraulic elevators (as illustrated) are a new branch that can be seen as adding elevators to old buildings of less than 10 floors without the need to build an additional machine room on the roof with a lift box。
1. Hydraulic plugs rise through sliders and wire-led sedans, as illustrated. How many metres do the hydraulic pips have to rise in order to lift the limousine?
2. There is a hydraulic elevator with a limousine of 1,300 kg of its own mass, a pump of 2. 3 x 106 pascal, and a compressor plume of 60, 85, 105, 140, 184, 238 six diameters (mm). The calculation indicates which diameter plugs should be selected. (as a result of the gravity of the cylinder itself and the need for a greater pull when the sedan tank accelerates up, the manufacturer provides for an extension of the diameter of the plume to 1. 4 times the calculated value, which is then selected from the six specifications given
Vii. (8) minutes
The density of wheat varies slightly from variety to type, from origin to origin, although the wheat is full, with different proportions of the various components and the strength of the grain. Use the instruments used in the course of the experiment to design a programme of experiments to determine the density of grain filled with grains, which provides:
1. Identification of the equipment, measurement components and operations required to reduce errors;
2. Formulas for the calculation of wheat density are written in letters representing physical volume。
Viii. (8 minutes)
Thermal showers are divided into water storage and water-free tanks. Water-storage showers take a long time to heat up the water in the water tank and to wait for hot water showers in the water tank when the water temperature has reached the required temperature. Water-free showers allow cold water to flow through the heater to reach the required temperature and flow immediately out of the vent for showers. Please use the following data to show that the use of water-free electric thermal showers in the home is not appropriate。
Cold water at 16°c
Hot water temperature for shower 38°c
4x10-3m3/ min
Water relative to heat 4. 2 x 103 j/kg degrees
Home lighting circuits allow the maximum power flow of about 5 ounces. Peasant
