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Selina Solutions Class 9 Physics Solutions for Exercise 5C in Chapter 5 - Chapter 5 Upthrust In Fluids Archimedes Principle And Floatation

Question 2 Exercise 5C

A body is held immersed in a liquid. (i) Name the two forces acting on the body and draw a diagram to show these forces. (ii) State how do the magnitudes of two forces mentioned in part

(i) determine whether the body will float or sink in the liquid when it is released.

(iii) What is the net force on the body if it (a) sinks, (b) floats?

Answer:

The two forces that act on the body are:

Downward direction – weight of the body

Upward direction – upthrust of the liquid

Selina Solutions CONCISE Physics - Class 9 ICSE chapter Chapter 5 Upthrust In Fluids Archimedes Principle And Floatation Question 2 Solution image

(ii) Magnitude of the forces acting on the body can determine whether the body will sink or

float.

The body will sink if the weight of the body is greater than the upthrust acting on it

whereas the body will float if the weight of the body is equivalent to or lesser than the

upthrust acting on it.

(iii) (a) The net force acting on the body when it sinks is the weight of the body itself.

(b) The net force acting on the body when it floats is the upthrust due to the liquid.

Video transcript
"hello everyone welcome to leader learning i am gurpreet your science tutor today's question is a body is held immersed in a liquid name the two forces acting on the body and draw a diagram to show these forces secondly state how do the magnitudes of two forces mentioned in a part determine whether the body will float or sink in the liquid when it is released thirdly what is the net force on the body if it sinks or floats so here in this question we are going to discuss what are the two forces which act on the body when it is immersed in a liquid okay next we are going to tell what happens to the body whether it will float or sink when it is released in the liquid or what is the net force on the body when when it sinks or when it floats so let's start our answer for the part a name the two forces that acts on the body the two forces are weight of the body firstly is weight of body next is your up thrust okay you can see in the picture the weight of the body is acting downwards and the up thrust is acting upwards okay so the two forces which are acting on the body are weight of the body and up thrust of the liquid now for the second part that is magnitude magnitude of the two forces here the magnitude of force is here the magnitude of forces determines whether the body will float or sink okay now in what conditions the body will float and in what conditions the body will sink if the weight of body is greater then up thrust then it will sink and if the weight of body is lesser that is up thrust is greater here then it will float okay so this is what the magnitude of two forces decide now for the third part that is net force acting on the body if it sinks for the third part when it will sink it will sink when the net force net force is equals to the weight of body okay then the body will sink but when the net force is equals to the up thrust then the body will float for more such videos please subscribe leader learning and for any doubts drop a comment thank you"
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