# (i)A block of steel of size 5*5*5 cm ^3 is weighed in water.If relative density of steel if 7,its apparent weight is ?(ii)When an object of mass 200 kg placed on an ice block floating on water it just sinks.The mass of ice berg is (Relative density of ice = 0.9,relative density of water is 1.02)please explain the 2 questions with proper explanation and steps.Waiting for answers.

1
by rajusetu

## Answers

2014-11-14T16:46:49+05:30

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1.  relative density = 7
It means for the same volume, steel weighs 7 times as compared to water.  The force of buoyancy will be equal to the weight of water displaced.

weight of steel block in water = weight in air - buoyancy force upwards
7 gm/cm³ * 125 cm³ * g  - 1 gm/cm³ * 125 cm³ * g =  0.750 * g Newtons
g = acceleration due to gravity = 9.81 m/sec²
if you want to write weight in kg, then  apparent weight = 0.750 kg

2.  let mass of ice berg = m.  When the object is placed on the ice berg, the total weight is just more than the buoyancy force.
total weight of ice + object = volume of water displaced * density * g
(m + 200 ) g = (m/0.9) * 1.02 * g

m+ 200 = m * 1.02/0.9 = 1.133 *  m

m = 200 / 0.133 = 1,500 kg