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Q1. The volume of 50g of a substance is 20cm3 . If the denstiy of water is 1 g cm3, will the substance float or sink in water ? justify your answer ?

Q2. Show that the energy of a vibrating pendulum is conserved ?

Q3. A ball is dropped from a heigh of 10m. If the energy of the ball reduces by 40% after striking the ground, how much high can the ball bounce back ?

1.volume of substance= 20 cm3

mass of substance= 50 g

density of substance = mass/volume

  =50/20

  = 2.5 g/cm3

density of water = 1 g/cm3

2.5 >1

density of substance > density of water

therefore the substance will sink in water.

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dencity of water=1 g/cm3

mass=50gm

volume=20 cm3

dencity of substance=m/v

50/20=2.5 g/cm3

so it will sink.

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thnx for the formula. not the person who asked this question but it helped me.

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Atitude
 
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 If the density of an object is more than the density of the liquid in which the object is placed the object will sink, if it is less the object will float.    density of object = Mass/ volume = 50/ 20 = 2.5 g/cm^3  The density of water is 1 g/cm^3. So, the object will sink. 
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 If the density of an object is more than the density of the liquid in which the object is placed the object will sink, if it is less the object will float.    density of object = Mass/ volume = 50/ 20 = 2.5 g/cm^3  The density of water is 1 g/cm^3. So, the object will sink. 
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pancakes
 
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and maple syrup
are tasty
:-)
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it will sink
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hmm..everybody's right...
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Density = mass / volume
mass = 50g
volume = 20 cm3
Density = 50 /20 = 2.5 g/cm3
If the density of a  substance is more than the  density of water it sinks.
Here , ​density of a  substance > ​density of water
That is , 2.5 g/cm3 >1 ​g/cm3
Therefore , it sinks.
 
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volume = 20 cm3
mass = 50 g
density = mass
              volume
             = 50 = 2.5 g/cm3
                20
density of body (2.5g/cm3) >  density of water (1 g/cm3)
        therefore, the body will sink in water 

hope it helps......
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Why it sink
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ANSWER 1:
​​​​​​Mass = 50g
volume = 20cm³
density = mass/volume = 50/20 = 2.5 g/cm³
density of water = 1 g/cm³

Since the density of the substance is greater than the density of water, it will sink in water.

The volume of water displaced = 20 cm³
mass of water displaced = volume×density = 20×1 = 20g
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ANSWER 2:
When the ball is dropped from a certain height, it will have some stored gravitational energy. This energy can be shown by 

 GPE = m x g x h

 The potential energy of gravity is directly affected by the height. When the ball is dropped from a 10m height, it loses 40% energy thus affecting the same percentage of height when it bounces back. 

Now 40% of the energy lost means 40% of the height also lost on bouncing back. Given height is 10m and when you lose 40% of 10m, left will be 60% of 10m. 

 The height of the bounce back is hence 60% of 10m which 6m.
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