Q.1. How the bats make use of ultrasonic waves to catch their prey? Explain?
Ans. The bat produces high pitched ultrasonic waves. The waves on striking the insect return back, which is heard by the bat. On hearing the echo the bat locates the insect and catches it. Q.2.How does the stethoscope help the doctors in listening to the sound of the patients heart beat? Ans. In a stethoscope, the sound produced within the body of a patient is picked up by a sensitive diaphragm and then reaches the doctor's ear by multiple reflections. Q.3. Explain how defects in a metal block can be detected using ultrasound. Ans. To detect minor cracks or flaws in metal block, ultrasonic waves are allowed to pass through metal blocks and detectors are used to detect the transmitted waves. If there is a crack in metal block, these waves get reflected back Q.4. How is ultrasound used for cleaning? Ans. The object to be cleaned is put in a tank fitted with ultrasonic vibrator. The tank is filled with cleaning solution. As the ultrasonic vibrator is switched on, high frequency vibrations are set up and the dust, grease and dust particles get detached and the object gets thoroughly cleaned. Q.5. What is echo ranging? State any one application of this technique. Solutions for Class 9th Science: Chapter 12 Sound Download File CBSE NCERT IX-Physics for term-II Chapter: Sound key points Read Full Post
2 Comments
CBSE Chapter: Structure of an Atom IX Chemistry assignment
Q.1. What are Canal rays? Q.2. On the basis of Thomson’s model of an atom explain how the atom is neutral as a whole. Q.3 Draw a sketch of Bohr’s model of an atom with three shells. Q.4. Helium atom has atomic mass of 4u and has two protons in the nucleus. How many neutrons does it have? Q.5. If the K and L shells of an atom are full, then what would be the number of electrons in the atom? Q.6. If the number of electrons in an atom is 8 and the number of protons is also 8, then; (i) What would be the atomic number of the atom? (ii) What is the charge on the atom? Q.7. Na+ ion has completely filled k and L shells. Explain. Q.8. The average atomic mass of a sample of element X is 16.2 u. What are the percentages of isotopes 16 X8 and 18 X8 in the sample? Q.9. If Z=3, what would be the valency of the element ? Also, name the element. Q. 10. Composition of the nuclei of two atomic species X and Y are given as under X Y Protons = 6 6 Neutrons = 6 8 Give the mass numbers of X and Y. What is the relation between the two species ? Q.11. Why do the elements helium, neon and argon have zero valency ? Q.12. Why do elements which exist as isotopes have fractional atomic masses ? Q.13. Are mass number and atomic mass of an element equal in all respects? Q.14. The element ALuminium is written by the symbol 27 13 Al. Write the number of protons, electrons and neutrons present in it. Q.15. The electronic configuration of an element Z is 2, 8, 6. How many electrons does it require to have a stable configuration? Q.16. Two atoms A and B have the following composition: Atom A Atom B 17 protons 17 protons 18 neutrons 20 neutrons What are their mass numbers ? What is the relation between the species ?Q.17. The composition of two atomic particles is given : X Y Protons 8 8 Neutrons : 8 9 Electrons : 8 8 (i) What is the mass number of X ? (ii) What is the mass number of Y ? Q.18. Briefly describe the features of the Rutherford Model of an atom. what are the drawbacks ? Q.19. How do isotopes and isobars differ? Write three applications of isotopes. Q. 20. What observations in scattering experiment led Rutherford to make the following conclusions: (i) Most of the space in an atom is empty. (ii) Whole mass of an atom is present in its centre. (iii) Nucleus is positivity charged. Q.21. Explain why did Rutherford select a gold foil innhis alpha-ray scatering experiment. Q.22. The atom of an element ‘A’ has three electrons in the outermost shell. It loses one of these to the atom of another element ‘B’. What will be the nature and value of charge on the ion which results from ‘A’ Q.23.The atomic numbers of atoms of two elements are 18 and 20 respectively and their mass numbers are 40. What is the name that can be given to such pairs of atoms. Will they have same chemical characteristics? Q. 24. Give reasons for the following: (a) Isotopes of an element are chemically similar. (b) An atom is electrically neutral (c) Noble gases show least reactivity (d) Nucleus of an atom is heavy and positively charged. (e) Ions are more stable than atoms. Q.25. which of the two will be chemically more reactive; element X with atomic number 17 or element with atomic number 16 ? Further Study related link Solved Summative Assessment Paper Solved some important questions for coming CBSE Exam How was the neutron discovered? How was the proton discovered? How was the Electron discovered? Extra mark’s Notes, "Atomic Structure" How was the Nucleus discovered? Downloadable study material: JSUNIL TUTORIAL 9th Chapter- work and Energy-Activity based Question Solutions
1. Is work done when you are reading book? Ans: No ,it is because there is no displacement in body. 2. Are you doing work when you are pushing wall or huge rock? Ans: No work is done as rock does not move. Energy using this time is converted as heat energy in body. 3. Give an application where a body displaces without application of work? Ans: Object displaced itself on inclined plane without application of work. 4. Idenfy two situation where object does not show displacement by the application of work? Ans: The two situations are: (i) if you push a mighty object (ii) If balanced force act on a body 5. Name an energy cause by sun? Ans: Hydroelectricity. 6. Name the two source of energy which are not due to sun? Ans: Nuclear energy and Geo thermal Energy 7. What happen if you are doing work without changing velocity of object? Ans: You work is stored in the form of potential energy. For example: When you compress slinky work done get stored in the form of Elastic potential energy. 8. Write the expression for power for a body having constants speed? Ans: P = Work /velocity 9. How can you say that sun is cause of hydro electricity? Ans: Solar energy evaporates water and help to form clouds. Cloud get down on the earth as rain. This water runs in river that is store in dam at high altitude. When this water allow falling rotate turbine and generating electricity. Thus that sun is cause of hydro electricity. 10. How is the dropping of ball from height is the an example of conservation of energy? Ans: When ball is dropped from high its gravitational potential energy decrease and at same time kinetic energy increases as it gain speed. Related Blog posts for edu. gainer 9th work and Energy-Activity based Question Solutions 9th Work Energy and Power solved Guess Questions IX Work Power and Energy Questions and Solution IX Work, Energy and Power: Notes: Study guide CBSE Work, Energy and Power - Assignment WORK, POWER AND ENERGY Guess Paper – 2012 Laws of conservation of energy -9th physics Numerical based on work and energy Class IX Work Power and Energy notes(Physics) Does every time when H2 and O2 combine, form only water?
Not every time. The product of any reaction depends on the condition the reactions i.e. temperature, pressure, catalyst etc... 2H2+O2→2H2O (water) Apart from water, H2 and O2 combine to form hydrogen peroxide(H2O2) also. H2+O2→H2O2 (hydrogen peroxide) The mass of a particular substance is remain same even 1 mole of atom or 1 molecules of of any substance contains 6.022 ×10 23 atom /molecules justify? Atomic mass or molecular it is expressed in g mol-1 i.e. it is the mass of 1 mole (6.03x1023) of atoms or molecules which is always a fixed quantity. For example.. Molecular mass of H2O is 18 g i.e. mass of 1 mole (6.03x1023 ) water molecule = 18g Mass of 1 water molecule = 18/6.03x1023 = 2.988 x 10-23 g And We know that 1 g = 1/ 1.66 x10-24 amu So 2.988 x 10-23 g =(2.988 x 10-23 g) /1.66 x10-24 amu = 18 amu or 18 u What is atomicity? Atomicity of ion may be defined as the number of atom present in that ion . For example.. · Al3+ atomicity is 1. · O2 - atomicity is 2. Atomicity is the number of atoms of an element present in one molecule of that element. For example, there are 2 atoms of hydrogen present in H2 molecule. So its atomicity is 2. The gases can be Monatomic, example: Helium (He)Carbon (C) Diatomic, example: hydrogen (H2) tri atomic , example: ozone (O3) Polyatomic, example: sulphur (S8). Give some examples of non ionic compounds? Non ionic compounds... CO2, C6H12O6, C6H6, CH4 How does the seventh postulate of Dalton's satisfy laws of constant proportional? The seventh postulate of Dalton's law states that In a given compound, the relative number and types of atoms are constant. The above statement means that the number of atoms of different elements in a compound is fixed and does not vary. We can say that the composition of a compound is fixed as same atoms will always combine in the same ratio. Thus a molecule of water will always have 2 atoms of hydrogen and one atom of oxygen. Remember: The postulate of Dalton’s atomic theory that “atoms can neither be created nor be destroyed” was a result of the law of conservation of mass. What is the mass of 0.5 mole of Cl2 gas? Molecular mass of Cl2 = 2 x atomic mass of Cl = 2 x35.5 =70 u Mass = molar mass x number of moles= 70u x 0.5 = 35.5 u NCERT Solutions for CLass 9th Science IX Chapter For Science Test Paper And Study Materials links Chapter: 3 Atoms and Molecules Chapter:4 Structure of the Atom YOU MUST VISIT THIS USE FULL LINK 9th chemistry Self-evaluation on Mole concept Numerical based on mole concept 9th ChemistryAtoms and Molecules MCQ 9th CBSE Science Chap 3 Atoms and Molecules Self study 9th Atoms and Molecules - Mole Concept and Problem 9th Atoms and Molecules Downloads Q.1. Can kinetic energy of a body be negative?
No as m ass and velocity cannot ne negative Q.2. A freely falling object eventually stops on reaching the ground. What happens to its kinetic energy? A freely falling object just before hitting the ground has maximum kinetic energy. After falling, it rolls on the rough ground and finally comes to rest. The kinetic energy of the object is used up in doing work against friction; which finally appears as heat energy. Q.3. Find the energy in kWh consumed in 10 hours by four devices of power 500 W each. Energy consumed = Power x time taken = 2000W x 10 h = 20000 Wh = 20 kWh. Q.4. Calculate the work required to be done to stop a car of 1500 kg moving at a velocity of 60 km/h? The work required to be done to stop a car = ( ½ mu2) - ( ½ mv2)= ½ m(u2-v2)= 1/2x1500(602-0)=2.08J Q.5 What is the work done by the force of gravity on a satellite moving round the Earth? Justify your answer. The work done by the force of gravity on a satellite moving around the Earth is zero. When a satellite moves around the Earth in a circular path, then the force of gravity acts on it directed towards the centre. The motion of the satellite is in the horizontal plane. Therefore, the force of gravity of Earth on the satellite and the direction of motion of satellite are perpendicular to each other. Therefore, net work done = Fs cos 90 = 0. Q.6. The potential energy of a freely falling object decreases progressively. Does this violate the law of conservation of energy? Why? During the free fall of the object, there is continuous decrease in potential energy. This decrease in potential energy appears as an equal amount of increase in kinetic energy. Thus, the sum of the potential energy and kinetic energy of the object would be the same at all points. That is, potential energy + kinetic energy = constant. According to the law of conservation of energy, the total energy of system remains unchanged. Thus, the given statement does not violate the law of conservation of energy. Define 1 J of work. Work done = Force x Displacement If force, F = 1 N and displacement, s = 1, m then the work done by the force will be 1 Nm or1 J. Thus, 1 J is the amount of work done on an object when a force of 1 N displaces it by 1 m along the line of action of the force. Download other study material on Work, Energy And Power |
Blog SeaRCH Link
All
Join Us For Update |