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## Thursday, February 16, 2012

### 9th ASSIGNMENT FOR THE SESSION 2011-2012 Science and technology

CBSE PHYSICS: ASSIGNMENT FOR THE SESSION 2011-2012 Class: IX Sub...
JSUNIL TUTORIAL: Section A : Physics
Q.1. Define work energy and power. Give the proper SI units. Hence derive the expression for kinetic and potential energy.
Q.2. State and prove the principle of conservation of energy. Also prove work energy theorem.
Q.3. A boy is moving on a road against a frictional force of 5N. After travelling a distance of 1.5km,he forgot the correct path at a roundabout (figure) of radius 100m. However he moves on a circular path for one and half cycle and then he moves forward upto 2 km. Calculate the workdone by him.
Q.4. Weight of a wooden piece is 6 kg.While floating in water its 1/3 rd volume remains submerged in
water. Calculate the maximum weight that may be placed on it so that it may float completely submerged.
Q.5. When a boat floats in water its one fourth volume remains submerged. The maximum weight that can be placed on boat is 1200 kgf. Calculate the weight of empty boat.
Q.6. Explain the working and application of a SONAR. How defects in ametal block can be dected using ultrasound.
Q.7. A stone is dropped from the top of a tower 500m high into a pond of water at the base of the tower. When is the splash heard at the top? Given, g=10m/s2 and speed of sound =340m/s.
Section B : Chemistry
1. Calculate the mass of : a) 0.5 mole of silver b) 0.5 mole of sugar (C12H22O11). (Given atomic
masses are Ag = 108, C = 12, O = 16, H = 1)
2. Calculate the a) the number of atoms in one gram of gold b) the number of molecules in a drop of water weighing 0.05g.(atomic mass of gold = 197u) 1 x 1022 atoms of an element X are found to have a mass of 930mg. Calculate the molar mass of the element X.
3. What is the difference between the atomic mass and gram atomic mass of an element?
4. What are the limitations of Dalton’s atomic model?
5. What are the draw backs of Rutherford’s atomic model?
6. What are the salient features of Bohr’s atomic model?
7. What are the postulates of Dalton’s modified atomic theory?
8. Write the electronic configuration of the isotopes of chlorine and isobars of Ar, Ca.
9. The average atomic mass of a sample of an element X is 16.2 u. What are the percentages of isotopes of oxygen 16 and 18 in the sample?
10. A Bromine atom is available in the form of two isotopes. 79Br (49.7%) and 81Br (50.3%). Calculate the average atomic mass of Bromine atom. The atomic no. of Bromine is 35.
11. No. of protons, neutrons and electrons in four spaces A, B, X and Y are respectively 6, 6, 6; 7, 7,7; 6, 8, 6; and 9, 10, 10. Give symbolic representation of each species and tell which of them are isotopes and which are isobars.
12. What do you mean by radio isotopes? Give two applications of isotopes.
13. Differentiate between isotopes and isobars. Write the application of the following isotopes:
a) U-235, Co-60, P-32 and I-131.
14. Atomic no. of Na is 11 and mass no. is 23. What type of ion will be formed by it and how will you represent it? Calculate the no. of electrons, neutrons and protons in the ion formed.
15. An ion X-2 contains ten electrons and 8 neutrons. What are the atomic no. and mass no. of element X? Name the element.
Section C : Biology
CHAPTERS - BIOLOGICAL DIVERSITY, HEALTH & DISEASES, OUR ENVIRONMENT
(BIOGEOCHEMICAL CYCLES, GREENHOUSE EFFECT)
1. What is evolution? How is algae different from fungi? Draw diagram of any one member of Protista.
2. How are pteridophytes different from bryophytes? Write any four differences between angiosperms and gymnosperms.
3. Write the differences (any four) between the following groups a) poriferans and coelenterates b) molluscs and arthropods c) flatworms and roundworms d) aves and mammals
4. Explain the different means by which infectious diseases spread in the environment? List the preventive measures of such diseases.
5. Justify, why it is difficult to make antiviral medicines than antibacterial medicines.
6. Explain the different processes involved in oxygen and water cycle operating in nature.
7. Represent schematically the carbon and nitrogen cycle operating in the biosphere. How is carbondioxidefixed in environment?