social science class 10............. . ......
Answers
Answer:
Please make brain list
I am also in 10
Explanation:
We have 10 answers here , all are same , but if we think more ,the answer could be different. Here we consider only mass (20 kg) of object, not its size. But i think that we must not neglect the size of the object.
Now suppose this object has height 1 m and width 0.5 m and also suppose that it has two parts , lower part ( 10 kg ) , upper part ( 10 kg ) so combined together it is 20 kg and 1 m height.
We can calculate the potential energy of the object as whole or seperately of two different parts.
Here we calculate in second way
Lower part is 10 kg so
10×9.81×20 = 1962 j
Now upper part is also 10 kg but it is above the lower part and lower part has height 0.5 m , so the total height for upper part is 20.5 m so
10×9.81×20.5 = 2011.05 j
So the total potential energy gain of object is
3973.05 j
Energy required to raise the 20 kg mass to the height 20 m is 20×9.81×20 = 3924 j
Above calculation shows that gravitational potential energy of the object is more than the energy required to lift that object to that particular height.
So , it is violating the mechanical energy conservation , energy conservation.
Similarly if we use the potential energy of those two parts of that 20 kg object seperately ( one after another ) to check the mechanical equivalent of heat then there will be a variance in work done and heat generated. It will not be directly proportional.
To explain the above facts , i have imagined an example . This example shows the difference between both the energies. For understanding , first we take general example for potential energy.
Please see the below picture ( Example 1 )
As shown in figure , suppose we have a 10 kg mass resting on the ground. Now i lift this mass upto 1 meter height and keep it at rest at that height.
Now we calculate the energy ( E ) required to lift this mass upto 1 meter height.
So E = mgh , here
m is mass
g is gravity
h is height , so putting the values
E = 10×9.81×1
E = 98.1 joules.
Now we calculate the potential energy ( PE ) of this mass when it is at rest at 1 meter height above the ground.
So PE = mgh , here also
m is mass
g is gravity
h is height , putting the values
PE = 10×9.81×1
PE = 98.1 joules , so E = PE
It means that the energy required to lift any mass upto any height is equal to the potential energy of that mass at that particular height . So , both energies are always same.
Now we discuss about the Example 2 which shows that the potential energy of the lifted mass is more than the energy which was required to lift that mass.
Please see the attached picture (Example 2 )
As shown in the picture , there is a pipe.
Height is 1 feet or 12 inches
Diameter is 6 inches
It has a plunger at the bottom and a bowl attached to the top corner.
Bowl is 8 inches above the ground. Bowl diameter is 6 inches and height is 4 inches. Pipe is fully filled with water. As per the dimensions ( 6" diameter and 12" height ) of the pipe , the amount of water in pipe is 5.56 litre.
Now suppose i lift the water ( mass ) up by pushing the plunger in upward direction. When i push the plunger in upward direction , the water overflows from the top open end of pipe and goes to the attached bowl.
Suppose i pushed the plunger upto 4 inches .
The energy ( E ) required to lift the water (mass) upto 4 inches is
E = mgh , putting the values , ( 4 inches = 0.1016 meter )
Consider 1 litre = 1 kg
E = 5.56×9.81×0.1016
E = 5.54 joules
Plunger is pushed upto 4 inches , so as per dimensions ( 6" diameter and 4" height ) the amount of water overflow ( Displaced ) is 1.85 litre. Now , the remaining water in the pipe is 3.71 litre. Here we see that , when the mass ( water ) is lifted , it splits into two parts.
Now we calculate the potential energy ( PE ) of the water ( mass )
1. Water in the pipe is 4 inches above the ground so , height is 4 inches = 0.1016 meter
PE of water in pipe ,
PE = mgh , putting values
PE = 3.71×9.81×0.1016
PE = 3.6977 joules
2. Water in the bowl is 8 inches above the ground so , height is 8 inches = 0.2032 meter
PE of water in bowl ,
PE = mgh , putting values
PE = 1.85×9.81×0.2032
PE = 3.6877 joules
So , total potential energy is
PE = 7.3854 joules
So from above calculations we see that the potential energy ( PE ) of the mass is more than the energy which was required to lift that mass.
So , we may say that when any mass is lifted , and if it splits into parts and those parts occupy different positions then , the potential energy gain of such mass is more than the actual energy which was required to lift that mass.