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plz anwser these questioins

a) If 2 equal weights of unequal volumes are balanced in air, what will happen when they are completely dipped in water?why?

b) A 12 kg sheet of tin sheet of tin sinks in water but if the same sheet is converted into a box or boat, it floats.why?

c)A body floats in kerosene of density 0.8*10kg/m3 up to a certain mark. If the same body is placed in water of density 1.0*10kg/m3 , will it sink more or less?why?

d) Woode sleepers are kept below the railway line.why?

e) a wide steel belt is provided over the wheels of an army tank.why?

(a) When a body is placed in a liquid a buoyant force acts upward which is equal to the weight of volume of liquid displaced by the body.  If the buoyant force is equal to the weight of the body then the body will float otherwise it will sink.When two bodies of same mass but different volumes are immersed in the liquid then the body with larger volume displaces more liquid and the buoyant force acting on it in upward direction is more. So, depending on the volumes of liquid displaced the two bodies, they may sink or may float. Also the apparent weight of the body with larger volume will be smaller than the apparent weight of the body with smaller volume.

(b)As the weight of volume of water displaced by the tin container is greater than the weight of tin. Thus the buoyant force acts upward and balances the tin container while in case of tin sheet, the buoyant force is not enough to balance it thus it sinks.

(c) As the density of water is higher than kerosene, less volume of  displaced water will required to balance the weight of the  body, thus the body will sink less in water than in kerosene. 

For answers of (d) and (e) you can refer the solutions given by Vasanthraj.

@vasanthraj: Your answers are appreciable.Keep it up.

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 a) their density varies because volume is a factor determining density

b)as its volume increases for same mass it floats. volume is inversely proportional to density, therefore density decreases when volume increases.

c)as density of water is more than that of kerosene, the object will sink less in water and more in kerosene

d) this is because wooden sleepers increase the area on which pressure of train is to be exerted, thus pressure is not concentrated on a single point densely.therefore if there more area there would be less pressure and train will run smoothly

e) an army tank is so hevy therefore it can cause depression in the place where it moves. therefore, to decrease pressure steel belt is provided over wheels of army tank

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