1 The following measures can reduce the pressure:
A. make the strap of the schoolbag wider B. the straw of the soft-packed pigment has its end sharpened C. sharpen the blunt edge of the knife, axe or scissors
D. change a brick on the horizontal ground from a flat to a vertical position.
2. The buoyant force on a stone sinking in water is:
A. increasing B. decreasing C. unchanged D. indeterminable
3. A ball with a mass of 0.2 kg is thrown into a container full of water, and 0.16 kg of water overflows, after coming to rest the ball will be:
A. sunk in the bottom B. suspended in the water C. floating out of the water D. floating out of the water C. float out of the water D. can not be determined
4. the same object has floated in kerosene, water, salt water, compare the three cases, the size of the buoyant force on the wooden block:
A. kerosene in the largest B. water in the largest C. salt water in the largest D. the same as the largest
5. a homogeneous object suspended in the water, such as it will be truncated into two unequal sizes, then:
A. the larger underneath, the larger underneath, the smaller underneath.
A. the larger sinks and the smaller floats B. neither sinks C. both float D. both float
6. The following vehicles use air buoyancy to lift off the ground:
A. helicopters B. airships C. jet planes D. rockets
7. A block of wood weighing 10N floats on the surface of the water, with 2/3 of its total volume exposed to the surface of the water, and to make it completely submerged in the water, a vertical downward force should be applied to it. A. 30N B. 20N C. 10N D. 5N
8. After the submarine is fully submerged, it continues to dive, when it is subjected to buoyancy and pressure:
A buoyancy remains constant, pressure remains constant B buoyancy remains constant, pressure increases
C buoyancy increases, pressure remains constant D buoyancy decreases, pressure decreases
9. p>9. A, B two identical cylinders filled with two kinds of liquids, a ball were put into the cylinder A, B cylinder, the ball in the cylinder A suspended, in the cylinder B floating (liquid did not overflow), on the A, B two cylinders of the density of liquid ρ A, ρ B the relationship between the correct:
A ρ A = ρ B B ρ A> ρ B C ρ A < ρ B D can not be judged
10. >10. In the teaching of "atmospheric pressure", when the teacher demonstrated the "bottle sucking eggs", the students had a heated discussion of this phenomenon, the correct analysis is:
A the mouth of the bottle due to the expansion of heat, so that the egg fell into the bottle B the bottle of gas to suck the egg into the bottle
C the egg by gravity into the bottle D the bottle fell into the bottle by gravity
C the bottle by gravity D the pressure of the gas inside the bottle decreases, the outside atmosphere pressed the egg into the bottle
11. about 1 meter long glass tube to do the Torricelli experiment, the following situation in the tube of mercury vertical height has an effect on:
A the thickness of the glass tube B the length of the glass tube
C depth of insertion of the glass tube D the height of the experimental location
12. As shown in Figure 1, there is a piece of ice in the cylindrical cup, the pressure of ice on the bottom of the cup P ice, ice dissolved into water on the bottom of the cup pressure P water, the two pressures compared (not counting the evaporation), then:
A P water> P ice B P water < P ice C P water = P ice D can not be compared
13. the following events, using the role of atmospheric pressure is:
A. use a peg to pin the map
B. A doctor uses a syringe to push medicine into a patient's muscles
C. A person breathes fresh air into his lungs
D. A deep-water diver wears a special pressure-resistant suit
14. The following statements are correct:
A. Objects made of substances with densities greater than that of water will definitely sink to the bottom of the water
B. Objects made of substances with densities equal to that of water cannot float on water
15. The object made of a substance with a density equal to that of water cannot float on the surface of the water
C. It is also possible for an object with a density less than that of water to be suspended in water
D. When solid iron and wooden blocks of equal mass are placed in water, the buoyancy of the iron block must be less than that of the wooden block
II. Fill-in-the-blanks (2 points for each blank, *** counting 40 points)
1. 54N/m2= _______Pa; 300Pa means ____________________________.
2. A brick weighing 20N is pressed against a vertical wall with a force of 50N; if the area of contact between the brick and the wall is 20cm 2 , the pressure of the brick on the wall is _______N and the pressure is _______Pa; the friction force on the brick is _______N.
3. The value of 1 standard atmospheric pressure is approximately equal to _______Pa, and the atmospheric pressure The value of atmospheric pressure decreases with increasing altitude, within 2000m above sea level, for every 12m of elevation, the atmospheric pressure decreases by about _______Pa.
4. At standard atmospheric pressure, piston pumps pump water at a height of no more than _______m. Centrifugal pumps use _______________ to pump water.
5. A ship that has been hung from the sea and sailed into a river, the magnitude of the force of gravity _______ on it, the buoyant force _______ on it, and the body _______ it displaces. (fill in "bigger", "smaller" or "unchanged")
6. Hanging on the spring scales of the iron block weighs 10N, when the iron block all invade the water, the spring scales of the number is 7N; at this time the buoyant force on the iron block is _______N, the volume of the iron block is _______m3.
7. The volume of 1m3 of a large square block of wood, floating on the surface of the water when there is a 3/5 of the volume of the water surface, then the buoyant force of this square block of wood is _______ square block of wood the mass of _______kg.
8. The mass of the hollow aluminum ball is 720g , which happens to be suspended in water, then the volume of the hollow part of the hollow aluminum sphere is _______cm3. (P aluminum = 2.7X 103kg /m3)
9. The object is subjected to a gravitational force of 5N and has a volume of 5×10- 4m3 . When it is submerged in water, the buoyant force on it is N. The combined force of buoyancy and gravity is N (g is taken as 10N/kg).
10. 1N weight of the wooden block floating on the water surface, the wooden block by the buoyant force is N, if the water to add salt, so that the density of the liquid becomes larger, then, the wooden block exposed to the liquid surface volume (choose "bigger", "smaller" or "no change"). "unchanged")
11. a piece of wood weighing 9.8N floating on the water surface, its density is 0.5 × 10kg / m, to be fully immersed in water, need to add ________N vertical downward force.
12. A ship from the South China Sea into the Yangtze River, the buoyancy (fill in the table "bigger", "smaller", or "unchanged"). Before and after the ship loaded with goods in Shanghai port, the ship's draft increased by 0.3m, the ship near the water surface of the horizontal cross-sectional area of an average of 5000m2, then the mass of the loaded goods kg.
13. giraffe is the world's tallest animal, so the giraffe is also the world's highest blood pressure of the animals, the giraffe blood density of about 1.05X 103kg/m3, when the giraffe heart contraction of blood pressure, the giraffe's blood pressure is the highest. Giraffe blood density is about 1.05X 103kg /m3, when the giraffe heart contraction of the blood pressure to the brain than the heart 3m high, the pressure is at least ______________Pa (g take 10N/kg).
III. Inquiry and answer questions (***22 points)
1, (4 points) a basketball floating in the still water, please draw a diagram of the force on the basketball.
2. A rectangular object, hanging it on a spring scale, shows 30 N. Submerging it in water, the spring scale shows 27 N. Find
(1) What is the volume of water displaced by the rectangular object in m3
(2) If the pressure of the liquid on its upper surface is 8 N, what is the pressure on the lower surface of the rectangular object in N?
(3) Submerging the When the rectangle is submerged in another liquid, the spring scale shows 27.6N, find the density of the liquid. (g=10N/kg)
3. A factory is building a chimney. Design of the chimney foundation covers an area of 4m2 built chimney weighs about 2.2x106N. intends to build a chimney where the chimney survey, measured here the ground can withstand the pressure of 5.0x105pa. asked: the chimney can be built according to the original plan? If not, and must be built in place, what measures can be used?