Group A
1. What is pressure?
Answer: Pressure is defined as the thrust acting per unit area of the surface of a body.
2. Write down formula and SI unit of pressure.
Answer: Pressure (P) can be calculated as the ratio of Thrust (F) to Area (A) or P = F/A. The SI unit of pressure is Nm-2.
3. What is thrust? Write down its SI unit.
Answer: Thrust is defined as the force acting perpendicular to the surface of an object. Its SI unit is Newton (N).
4. Name the two factors on which the pressure exerted by a body depends.
Answer: The pressure exerted by a body depends upon a) Thrust and b) Area.
5. What is hydraulic pressure?
Answer: The pressure exerted by liquid because of its characteristic incompressibility and definite volume is called hydraulic pressure.
6. On which factors does hydraulic pressure depend? Write.
Answer:
7. State Pascal’s law of liquid prerssure and write any one equipment based on this law.
Answer: Pascal’s law of liquid pressure states, “Pressure is exerted by a liquid equally in all directions when a force is acted upon it.” Hydraulic press is an equipment based on this law.
8. On which law is the given diagram based? State the law.
Answer: The given diagram is based on Pascal’s law of liquid pressure.
9. What is hydraulic press?
Answer:
10. Write down the principle of hydraulic press.
Answer:
11. What is hydraulic brake?
Answer:
12. Write down the use of hydraulic lift.
Answer:
13. Name the equipment shown in the given diagram. Also, write down the principle on which the equipment works.
Answer: The name of the equipment shown is hydraulic lift. It works on the priciple of Pascal’s law of liquid pressure.
14. Why is hydraulic jack used? Write.
Answer:
15. State Archimedes’ principle.
Answer: Archimedes’ principle states, “A body that is partially or totally submerged in a fluid experiences an upthrust equal to the weight of liquid displaced.”
16. Name any two instruments based on Archimedes’ principle.
Answer:
17. What is atmospheric pressure?
Answer: The pressure exerted by the atmosphere (air) is called atmospheric pressure.
18. What is barometer?
Answer:
19. What is syringe?
Answer:
20. What is upstroke?
Answer:
21. What is down stroke?
Answer:
Group B
1. Write two differences between force and pressure.
Answer:
2. Write two differences between pressure and upthrust.
Answer:
3. Write two differences between Pascal’s law and law of floatation.
Answer:
4. Write two differences between Pascal’s law and Archimedes’ principle.
Answer:
5. Write two differences between density and relative density.
Answer:
6. An iron nail sinks in water but a ship made up of iron floats. Why?
Answer:
7. An egg floats on saturated salt solution but sinks in fresh water. Why?
Answer: The egg kept in the beaker containing pure water sinks but that kept in the beaker kept in saturated salt solution floats on it. This is due to density of water, saturated salt solution and the egg. The density of egg is greater than pure water but less than that of saturated salt solution. Any object that has density more than the solution sinks in it. If its density is less than the solution or liquid, it floats on it. These are the cases of law of floatation.
8. An iron nail sinks in water but floats on mercury. Why?
Answer: The density of iron nail is more than that of water so it sinks in it. However, the desnity of iron nail is less than that of mercury so, it floats on it. This is due to the law of floatation that bodies can float on a liquid if they have less or equal densities as that of the liquid.
9. On which law the given experiment is based? Write with reason.
Answer: The given experiment is based on Archimedes’ principle. It is because the weight of water displaced is equal to the weight of student weighed in air which is in accordance with the principle.
10. It is easier to swim on the sea than on the pond, why?
Answer: It is easier to swim on the sea than on the pond due to the upthrust provided by the water. The density of sea water is more than that of the pond.
11. What is the difference between an empty ship and loaded ship moving on the sea water?
Answer: An empty ship has less weight compared to a loaded ship. So, a loaded ship displaces more sea water than an empty one. Hence, the water level rises higher when a loaded ship moves on the sea water as compared to when an empty ship moves.
12. An egg sinks in pure water but floats on solution of salt with water, why?
Answer: The egg kept in the beaker containing pure water sinks but that kept in the beaker kept in salt solution floats on it. This is due to density of water, salt solution and the egg. The density of egg is greater than pure water but less than that of salt solution. Any object that has density more than the solution sinks in it. If its density is less than the solution or liquid, it floats on it. These are the cases of law of floatation.
13. Why is it easier to lift a heavy stone under water than in air?
Answer: Upthrust exerted by air is negligible. However, under water, the stone is acted by an upward force – thrust which reduces the apparent weight of the stone and thus, we find it easier to lift a heavy stone under water than in air.
14. In the given figure, whcih is sea water and which is river water, why?
Answer: Fig 2 is sea water and Fig 1 is river water because the upthrust provided by the sea water is more than that by river water.
15. What will be the effect in the weight of displaced water if load is added into the ship floating in the ocean? Write with reason.
Answer:
16. Although a ship is made up of iron, it can float on water, why?
Answer:
Group C
1. On which principle does hydraulic brake base? Prove that the hydraulic press is a force multiplier.
Answer: Hydraulic brake is based on the principle of Pascal’s Pressure.
2. Why does a ball try to come up when it is pressed in water?
Answer: When we try to press a ball in water, water exerts an upthrust to the ball. This opposes our applied force. Thus, a ball tries to come up when it is pressed in water.
3. Answer the following questions after observing the given diagram of hydraulic press.
i) On what princpile does this machine work? State the principle.
ii) What role is played by water to multiply the force in this device?
4. Describe in brief the working mechanism of a syringe.
5. Describe the working mechanism of a water pump with figure.
Group D
1. Study the given figure and answer the following questions.
i) On which principle is the experiment based? State the principle.
ii) What is the weight of displaced water?
iii) What is the reason that the weight of the object is less in water than in air?
2. The ice made of water floats on water, why? Which instrument is show in figure? If cross-sectional area of piston A is 40 cm2 and that of piston B is 4 m2, what load is necessary on the piston ‘B’ to balance 600 N force kept on piston A?
3. Three objects with different densities A, B and C are in water as shown in the figure. Now, answer the following questions:
i) Which object has higher density than then water? Why?
ii) If the mass of object A is 1 kg. How much kg of water is displaced by the object?
iii)) Which law is applicable for object B? State the law.
4. A ship coming from sea enters the river, will its hull sink more or less in river water? GIve reason. The weight of an object is 20 N in air, the weight of that object in the water is seen 12 N only then:
i) What is the value of upthrust on the object by water?
ii) What is the weight of the displaced water by it?
5. Study the given table and answer the following questions:
| Substances | Density (g/cm3) |
|---|---|
| W | 0.8 |
| X | 13.6 |
| Y | 1 |
| Z | 0.9 |
i) If volume of all substances is equal, which substance has the greatest mass?
ii) Among the substances in the table, which substance sinks in water, why?
iii) Among the given substances, name the substance that gives the least upthrust. Give reason also.
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