Chemical change: a reaction/event where the chemicals/elements present before the change are NOT the same molecules present after the change.
For example, combustion reactions such as the burning of wood or rubbing alcohol are examples of chemical change. The reactants before the combustion of rubbing alcohol are CH3O (rubbing alcohol) and O2 oxygen (oxygen). The molecules present after the combustion reaction are CO2 (carbon dioxide) and H2O (water vapor).
Physical Change: a change in structure or state of a substance but, after the change the material is the same material that we started with. One example would be breaking a glass bottle by dropping it. The glass is now in smaller pieces than when we started, but the glass molecules are still glass molecules.
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Solar energy ....................
Answer: (a) Smaller charge is
and larger charge is
.
(b) Smaller charge is
and larger charge is
.
Explanation:
(a) When both the spheres have same charge then force is repulsive in nature as like charges tend to repel each other.
Therefore, total charge on the two non-conducting spheres will be calculated as follows.

= 
Therefore, force between the two spheres will be calculated as follows.
F = 
12 N = 

or, 



This means that smaller charge is
and larger charge is
.
(b) When force is attractive in nature then it means both the charges are of opposite sign.
Hence, total charge on the non-conducting sphere is as follows.


Now, force between the two spheres is calculated as follows.
F = 
12 N = 



Hence, smaller charge is
and larger charge is
.
Answer:22537.92 J
Explanation:
Given
mass of karen 
Distance covered by Karen =69.6 m
acceleration due to gravity=9.8
inclination
vertically karen move

h=39.72 m
Work done by escalator on karen is equal to change in potential energy of karen

