Kerala Syllabus Class 9 Physics - Chapter 5 Buoyant Force - Questions and Answers
Questions and Answers for Class 9 Physics പ്ലവക്ഷമബലം | Text Books Solution Physics (English Medium) Physics: Chapter 05 Buoyant Force - Questions and Answers | SAMAGRA Question Bank
ഒമ്പതാം ക്ലാസ്സ് ഫിസിക്സിലെ Buoyant Force എന്ന പാഠം ആസ്പദമാക്കി samagra തയ്യാറാക്കിയ ചോദ്യോത്തരങ്ങള്.
Class 9 Physics Buoyant Force - Question Bank
∎Physics (English Medium Notes)
1. When an object is fully or partially immersed in a fluid, the upward force exerted by the fluid on the object is the --------------
Answer: buoyant force
2. What provides the buoyant force that allows a helium-filled balloon to rise in the air?
Answer: Air
3. An iron nail sinks in water because it has a greater ……..….. than the buoyant force exerted by the water.
Answer: Weight
4. Observe the figure. There are 4 objects in a glass of water and above it. In which of these objects is the water exerting buoyant force?
5. A 10 N weight is suspended from a spring balance and is submerged in water. The reading shown by the balance now will be ……..…..
(10 N, 12 N, 6 N, 0 N)
Answer: 6 N
6. Would a 100 N object feel heavier in water or glycerin?
Answer: In water
7. An egg is immersed in a beaker of water. Then, a large amount of salt is dissolved in the water without breaking the egg. What change will occur in the position of the egg?
(sink more, rise, remain the same, none of the above)
Answer: rise
8. An iron piece is completely immersed into an overflow jar filled with water. What will the decrease in weight experienced be equal to?
Answer: Equal to buoyant force / Equal to the weight of overflowed water
9. When an aluminium foil is shaped like a boat and placed in water, it floats. However, when it is rolled up and placed in water, it sinks. The reason is the difference in the ……..….. of the foil.
Answer: volume
10. The ……..….. of a substance is its mass per unit volume.
Answer: density
11. The ratio between the density of an object and the density of water is known as ……..…..
Answer: Relative density
12. The unit of relative density is ……..…..
Answer: no unit
13. Name the device used to measure the relative density of liquids.
Answer: hydrometer
14. Name the device used to measure the relative density of milk.
Answer: lactometer
15. The density of kerosene is 810 kg/m3. Find the relative density of kerosene.
Answer: 0.81
16. Why does a cup filled with water feel heavier when lifted from underwater and out of the water?
Answer: Due to the buoyant force of water acting on the object submerged in it, a decrease in weight is experienced on it
17. What is meant by Buoyant Force? Provide an example.
Answer:
• When an object is fully or partially immersed in a fluid, the upward force exerted
by the fluid on the object is the buoyant force.
• A stone experiences a loss of weight in water
18. What causes a helium-filled balloon to rise in the air?
Answer: Due to the buoyant force of air
19. State Archimedes' principle.
Answer: When an object is completely or partially immersed in a fluid, the buoyant force acting on the object is equal to the weight of the fluid displaced by the object. This is Archimedes’ principle.
20. State the Principle of Floatation
Answer: When an object floats on a fluid, the weight of the object and the weight of the fluid displaced are equal.
21. A boat on a lake displaces 6000 kg of water. Calculate the buoyant force experienced by the boat.
Answer:
weight of the displaced water = buoyant force
= 6000 kgwt = 6000 × 9.8 N = 58800 N
22. If an object weighs 0.45 kgwt in air and 0.31 kgwt when fully immersed in water, find the following.
a) The loss of weight of the object.
b) The buoyant force.
c) Weight of water displaced.
Answer:
a) The loss of weight of the object = 0.45 kgwt – 0.31 kg wt = 0.14 kg wt
b) The buoyant force = 0.14 kg wt = 0.14 × 9.8 N = 1.372 N
c) Weight of water displaced = 0.14 kg wt = 0.14 × 9.8 N = 1.372 N
23. The density of copper is 8900 kg/m³. What is its relative density?
Answer: The relative density of copper = 8900 kg/m³ ÷ 1000 kg/m³ = 8.9
24. What is the density of mercury if its relative density is 13.6?
Answer: The density of mercury = 13.6 × 1000 kg/m³ = 13600 kg/m³
25. Don’t you know that it is a crime to sell adulterated (water-added) milk? How will you know that water is added to milk? What is the device used for it?
Answer: Lactometer
26. What is the device used to measure the relative density of milk?
Answer: Lactometer
27. Will the reading be the same if a lactometer is placed in pure milk and water-added milk? Why?
Answer: No. Since the density of water-added milk is lower, the lactometer sinks more and shows a lower reading.
28. Is it in pure milk or fat-removed milk that a lactometer sinks more? Why?
Answer: Fat-removed milk has a lower density. So, the lactometer will sink more in fat-removed milk.
29. Using a lactometer, how will you identify whether water is added to milk?
Answer: The lactometer sinks more in milk to which water has been added.
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