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  1. J

    Why we can't hear ?

    If sound travels faster in solids than in air then why on closing our ears we cannot hear the sound properly?
  2. J

    Can i get to NASA?

    What is the scope of btech in PHYSICAL SCIENCES from IIST(indian institute of space science and technology)? after that course it is compulsory to work in ISRO for 5 years...(if you get first class) will that be enough to get into NASA?
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    Number of live viruses

    Homework Statement A virus give birth to 2 new virus in each second and life span of each virus is 5 seconds.The process of reproduction is continuous until the death of the virus.Initially there is one newly born virus at time t=0.Find the total number of live viruses just after 10 seconds...
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    Stuck with a problem in electrochemistry

    Homework Statement A galvanic cell consisting of two silver electrodes,one in a saturated solution of AgBr and the other in a saturated solution of Ag2CrO4 is prepared.Calculate the value of Ecell at 298K Given Ksp(AgBr) = 5x10-13 M2 and Ksp(Ag2CrO4)=2.4x10-12M3 Homework Equations to...
  5. J

    Function of salt bridge

    What is the function of salt bridge in a daniell cell?Why KNO3 is used in salt bridge ?
  6. J

    Interior angles of a regular polygon

    The number of sides of two regular polygons are in the ratio 5:4 and the difference between their interior angles is 6 degrees.Find the number of sides of the two polygons. I forgot the relation between interior angles and the number of sides of a regular polygon.Can anyone help me to figure...
  7. J

    De morgan's laws

    In my textbook, the proof for demorgan's law, (AintersectionB)* = A*unionB* [*=complement] starts with,saying that for all x belongs to (AintersectionB)* , x is not a member of AunionB. But how can we say that, for example, if A = {1,2,3} and B = (2,3,4,5} and U = {1,2,3,4,5}...
  8. J

    How the charges are transferred?

    "When we touch a pith ball with an electrified plastic rod, some of the negative charges on the rod are transferred to the pith ball and it also gets charged." I want to know how does this happen ?
  9. J

    How to get back my curiosity

    I'm afraid whether this place is best to post my question.But i need a help as soon as possible.At first,i was very curious to know things or to investigate more about the world. Studying was not at all a burden for me. It was almost a spontanoeus process that i used to read books and i didn't...
  10. J

    Isolated system

    "The charge of an isolated system is conserved" What is the meaning of isolated system ?
  11. J

    Electromagnetic waves

    When we heat a metal, the positive kernels begins to vibrate.Will this vibrations produce electromagnetic waves ?
  12. J

    Can we accelerate in space ?

    Imagine we are in a space craft which is moving with a constant velocity in empty space. If we are not influenced by any gravitational forces, and if we restart the engine, will it be accelerated ?
  13. J

    What is the physical significance of work?

    As the title suggests, what is work? Or, what is the physical significance of work? My textbook define work as crossproduct of force and displacement. But why do we need that quantity?
  14. J

    How torque, t = r x F ?

    how torque, t = r x F ? Or, what is the physical meaning of cross product of two vectors?
  15. J

    Distribution of charges

    When a charge is given to a metallic sphere it spreads in its entire surface area,and when a charge is given to an insulating sphere, it spreads over its entire volume.Why is it so?
  16. J

    Masses of fundamental particles

    How were the masses of fundamental particles(electrons,protons,neutrons) determined?
  17. J

    Charge leaks out?

    What is the meaning of the statement "charge leaks out"?Or how charge leaks out? As charge is a property, how can we say that a property leaks out?
  18. J

    Absence of an electron at a point creates a positive charge

    I can't understand how does the absence of an electron at a point creates a positive charge there. In my opinion, it is wrong on account of conservation of charge. Because if we consider an electron(at a point A) as a system, and if the electron get displaced to another point B(in the system)...
  19. J

    Exam question

    Q:Prove that a square matrix A is invertible iff A is non singular. My Ans: Since the inverse of a square matrix is given by, A^ = (1/|A|)adj.A (Where A^ is A inverse) If |A|=0, A^ is not defined. i.e, A^ exist only if A is non singular. In other words, a square matrix...
  20. J

    Unit cell

    Q.The unit cube length of LiCl (NaCl structure) is 5.14 amstrong . Assuming anion-anion contact, calculate the ionic radius for chloride ion. How to assume anion-anion contact ? Can any one help with a 3D figure?
  21. J

    Big bang

    I am having problem with understanding the concept of big bang theory. Actually I don't believe in the theory. How can we say that this universe was formed because of a big explosion? We can't answer the question what happened before that.
  22. J

    Number of roots

    Why is it said that an equation of nth degree must possess n roots ? if x^1 = y, x has only 1 value x^2 = y, x has 2 values (the 2 values may be equal) x^3 = y, x has 3 values going on like this, we have, x^0 = 1 , implies x has no solutions. but x has infinite number of solutions.
  23. J

    Matrix addition

    Ques.)-If A,B,C are three matrices such that A+B = A+C, then prove that B=C. Can i cancel out the A's in LHS and RHS ?
  24. J

    What is electrostatic potential

    I can't understand what actually is the electrostatic potential.The definition given in my textbook is as follows : "Electrostatic potential at any point in a region of electrostatic field is the minimum work done in carrying a unit positive charge from infinity to that point without...
  25. J

    Picture of galaxy

    How was we able to take the pictures of galaxies?
  26. J

    At. radii

    How does atomic radii decrease when we move left to right in a periodic table? Though the nuclear charge increase as a result of increase in number of protons,the same increase is occuring in number of electrons.
  27. J

    Newton's Third law

    I can't understand the significance of Newton's third law. What would happen if there were no reaction forces?
  28. J

    How the presence of d-orbitals affect size?

    In my textbook , it is given that Atomic radius of Ga is smaller than that of Al due to presence of d-orbitals in Ga. But how does the presence of d-orbitals reduces size?
  29. J

    Inert pair effect

    According to my text book,inert pair effect has two definitions 1:-The occurence of oxidation state which is two units less than the group oxidation is called inert pair effect. 2:-The reluctance of s-electrons to take part in bond formation is called inert pair effect. But both the...
  30. J

    Oxidation number

    I can't understand the term oxidation number.According to my textbook, it is the charge assigned to an atom. But for what purpose we are doing this?Is it for identifying the oxident and reductant in a reaction?If yes, on what basis the rules (for assigning oxidation states) are implemented...