The comprehensive approach in Kerala Syllabus 9th Standard Physics Notes Pdf Chapter 5 Buoyant Force Notes Extra Questions and Answers ensures conceptual clarity.
Kerala Syllabus Std 9 Physics Chapter 5 Buoyant Force Extra Questions and Answers
Question 1.
The weight of a piece of stone in air is 120 N and its weight in water is 100 N. Calculate the buoyancy experienced by the stone.
Answer:
Buoyancy = weight of stone in air – weight in water = 120N – 100 N = 20 N
Question 2.
What is the weight of water displaced by an object that weighs 100 N when floats on water. (100 N, Zero, More than 100 N, less than 100 N)
Answer:
100 N
Question 3.
A body that floated in water sinks when put in kerosene. Why did it happen?
Answer:
Kerosene has a lower density than water. So kerosene cannot exert more buoyancy when compared with water.
Question 4.
Observe the figures of an object placed in different liquids.
a) Compare the gravitational force and the buoyancy acting on the body when it is in liquids A and B.
b) Among A and B which ¡s the liquid whose density is greater than that of the object? Why?
Answer:
a) In the liquid A, buoyancy is greater than the gravitational force. In B, buoyancy is less than the gravitational force.
b) Liquid A. As the body floats, the density of the liquid is greater.
Question 5.
Kerosene and saline water are taken in two beakers. The same stone is immersed in both liquids.
a) in which liquid, more weight difference is experienced?
b) In which liquid, the stone experiences more buoyancy?
c) Write whether the buoyancy of that liquid is more or less than that of the other liquid?
d) What is the relation between the density of a liquid and buoyancy?
Answer:
a) In saline water
b) In saline water
e) More
d) Buoyancy increases with an increase in the density of a liquid.
Question 6.
X represents kerosene and Y represents water
Among A and B, which is the right figure? Why?
Answer:
B is the right figure.
Reason: The density of water is greater than that of kerosene. When taken in the same container due to the difference in density, water comes to the lower part and kerosene to the upper part.
Question 7.
An iron block of weight 2N is immersed in three different liquids: A, B, and C. The weight of the iron block experienced inside the liquids is labelled in the figure.
a) In which liquid the iron block experiences more buoyancy?
b) Among these three liquids, which has less density?
c) What is the relation between the density of a liquid and buoyancy?
Answer:
a) C
b) B
c) As the density of the liquid increases. buoyancy also increases. As density decreases, buoyancy decreases.
Question 8.
F1 and F2 represent two forces acting on an object immersed in water as shown in figure.
a) Name the two forces represented by F1 and F2
b) Define the force F2
Answer:
a) F1 – GravitationaL force
F2 – Buoyant force (Buoyancy)
b) When a body is immersed completely or partially in a liquid, the liquid exerts an upward force on the body. This force is known as buoyancy.
Question 9.
The weight of a stone in the air is 10 N. When it is immersed in water, it weighs 8N.
a) Why does the stone experience a loss of weight?
b) If the same stone is dipped in kerosene, what will be its weight? (8 N, more than 8 N, less than 8 N)
Answer:
a) It is due to buoyant force.
b) More than 8N
Question 10.
A body of weight ION sinks in water. The weight of the water displaced is 2 N.
a) What ¡s the weight of the object in water?
b) Which principle is related to this?
Answer:
a) 8N
b) Archimedes’ principle
Question 12.
An object of weight 500 N sinks ¡n water. The weight of the water overflowing is 50 N.
a) What is the weight of the object ¡n water?
b) If another object of the same weight floats on water, what ¡s the weight in water? What is the buoyancy? What is the loss of weight in water?
Answer:
a) Weight in water = Weight in air – weight of water over flowed = 500N – 50N = 450 N
b) When floats,
Weight in water = O N
buoyancy = 500 N
Loss of weight in water = 500 N
(When a body floats on a liquid, weight of the body in air = loss of weight = buoyancy = weight of water displaced)
Question 13.
What is the relation between the volume of the body and the volume of the displaced fluid when a body is fully immersed in a fluid?
Answer:
When a body is fully immersed in a fluid the volume of the displaced fluid will be equal to the volume of the body.
Question 14.
A body of weight 800 N sinks in a liquid. The weight of the liquid displaced is 200 N.
a) What will be the weight of the body ¡n liquid?
b) What is the buoyant force?
Answer:
a) 600N
b) 200N
Question 15.
The data given below is tabulated by Gokul while conducting an experiment to prove Archimedes’ principles. Fill the missing parts.
Answer:
a) 450 N
b) 30 N
e) 80 N
d)20 N
Question 16.
An object having weight 50 N floats on a liquid.
a) What is its weight in the liquid?
b) What is the weight of the liquid that is displaced?
c) What is the buoyant force?
d) Which is the law related to this, state the law.
Answer:
a) O
b) 50N
e) 50N
d) Law of floatation: Weight of a floating body is equal to the weight of the fluid displaced by it.
Question 17.
Give reasons
a) A ship floats on water.
b) When a body was placed in a liquid, it remained in the same position.
Answer:
a) Weight of the ship is equal to the weight of the displaced water.
b) The density of the object is equal to the density of the liquid, and buoyancy is equal to the gravitational force (weight of the body).
Question 18.
Complete the table related with Archimedes’ principle
| Object | Weight in air (N) | Weight in water (N) | Buoyant force | Weight of water displaced |
| Stone | 10 N | 8 N | (a) | (b) |
| Iron block | 15 N | (c) | 2N | (d) |
Answer:
(a) 2N
(b) 2N
(c) 13N
(d) 2N
Question 19.
body of weight 1000 N sinks in water. The weight of the liquid over flowed is 250 N.
a) What will be the weight of the body in water?
b) A body of the same weight as above floats in water. What ¡s its weight in water? What will be the weight of the water displaced?
Answer:
a) Weight of the body in water = 1000 N – 250 N = 750 N
b) Zero, 1000 N
Question 20.
Name the device used to measure the relative density of liquids.
Answer:
Hydrometer
Question 21.
Classify the following liquids into liquids having a density greater than that of water and liquids having a density less than water.
Honey, Glycerine, Saline water, Petrol, Diesel
Answer:
| Liquids having a density greater than that of water | Liquids having a density less than that of water |
| Honey | Petrol |
| Glycerine | Diesel |
| Saline water |
Question 22.
When a hydrometer is dipped in a liquid, the reading is found to be 1.25. What is the density of other liquids?
Answer:
Relative density = \(\frac{\text { Density of liquid }}{\text { Density of water}}\)
Density of liquid = relative density × density of water
= 1.25 × 100 = 1250 kg/m3
Question 23.
If the relative density of a liquid is greater than I
a) Which ¡s the liquid? (water/Kerosene/salt water)
b) What do you mean by relative density?
c) Which is the instrument used for finding relative density.
Answer:
a) Salt Water
b) It is the ratio of the density of the substance to the density of water.
c) Hydrometer
Question 24.
The density of liquid ethanol is 789 kg/m3. Calculate its relative density. (Density of water is 1000 kg/m3)
Answer:
Relative density = \(\frac{\text { density of liquid }}{\text { density of water}}\) = \(\frac{89}{1000}\) = 0.789
Question 25.
A hydrometer is placed ¡n water. The reading is one
a) What does this reading indicate
b) Does the reading increase or decrease when it is put in kerosene
c) State the principle of a hydrometer.
Answer:
a) It indicates the relative density of water.
b) Decreases
c) Principle of flotation: When an object floats on a fluid, weight of object is equal to the weight of the fluid displaced by it.