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प्रश्न
Why is a force needed to keep a block of wood inside water?
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उत्तर
A force is required to hold a block of wood in water because the upthrust caused by water on the block when fully submerged surpasses its weight.
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संबंधित प्रश्न
Define the term relative density of a substance.
How does the liquid pressure on a diver change if :
The diver moves horizontally?
The diagram below in Fig. 4.12 shows a device which makes the use of the principle of transmission of pressure.
- Name the parts labelled by the letters X and Y.
- Describe what happens to valves A and B and to the quantity of water in the two cylinders when the lever arm is moved down.
- Give reasons for what happens to valves A and B in part (ii).
- What happens when the release valve is opened?
- What happens to valve B in cylinder P when the lever arm is moved up?
- Give a reason for your answer in part (v).
- State one use of the above device.
A hammer exerts a force of 1.5 N on each of the two nails A and B. The area of cross section of tip of nail A is 2 mm2 while that of nail B is 6 mm2. Calculate pressure on each nail in pascal.
What do you understand by the term upthrust of a fluid? Describe an experiment to show its existence.
Describe an experiment to show that a body immersed in a liquid appears lighter than it really is.
Two identical pieces, one of ice (density = 900kg per meter cube) and other wood (density = 300kg per meter cube) float on water.
- Which of the two will have more volume submerged inside water
- Which of two will experience more upthrust due to water.
Pressure in a water pipe on the ground floor of a building is 100,000 Pa. Calculate the pressure in the water pipe on the first floor at a height of 3 m. [Density of water = 1000 kgm−3 ; g = 10 ms−2]
What is meant by up thrust?
What do you understand by the term “Buoyancy”.
