^{3}Kgm

^{-3}. What is the density of silver in SI unit?

^{3}Kgm

^{-3}

^{3}Kgm

^{-3}

__2. Is potential energy a vector or a scalar quantity?__

__3. (i) Give any two examples of longitudinal waves.(ii) What is the most essential property of a wave motion and why?__

__4. (a) Calculate the work done in lifting 200 kg of water through a vertical height 6 meter. (Assuming g = 10m/s²) (b) When an object moves on a circular path, what is the work done?__

__5.(a) Calculate the power of an engine which can lift 200 Kg of water to store in a tank at a height of 10 m in 4.9 s. Also express in horse power. (Given = 9.8m/s2) (b) What type of energy is stored in the spring of a watch? (c) What is the work done by the tension in the string of a sample pendulum?__

^{2}x 10 m

^{2}x 10 m]/ 4.9 s= 4000 W÷746 HP=5.36 HP

__6. The atomic number of chlorine is 17 and mass number is 35. a. What would be the electronic configuration of a negatively charged chloride ion, Cl__

^{-}? b. What would be the atomic number and mass number of Cl^{-}? c. Define valency and calculate the valency of Cl^{-}.^{-}) is formed when Cl gains one electron. So, Cl

^{-}has 18 electrons and 17 protons.

^{-}= 2, 8, 8

^{-}= Number of protons = 17 Mass number of Cl

^{-}will be the same as Cl i.e. 35

__7. The relative atomic mass of Boron is 10.8 u. Calculate the percentage of its isotopes__

^{10}B_{5}and^{11}B_{5}, occurring in nature.^{10}B

_{5}be y in the sample. The percentage of

^{11}B

_{5}will be (100-y)

^{10}B

_{5}and

^{11}B

_{5}, occurring in nature. 20% and 80%

__8. Give one example where kinetic energy is transferred from one object to other?__

__9. Define Avogadro’s constant. Give its value.__

^{23}

__10. (a) Chlorine occurs in nature in two isotopic forms with masses 35 u and 37 u in the ratio of 3:1. Calculate the average atomic mass of chlorine atom on the basis of this data. (b) Give any three uses of three isotopes.__

__11. When a person uses deodorant spray, the other person standing at a distance would hear the sound of spraying first and the fragrance of spray would reach him later. Why so?__

__12. Calculate the number of molecules of sulphur present in 16 g of solid sulphur.__

_{8}= 8 x 32 = 256 g

^{23}/256]x16 moles= 3.76 x 10

^{22}molecules

__13. Following observations were taken while determining the relative density of a liquid.__

__Weight of the solid in air = 0.100 kgf Weight of the solid in liquid = 0.080 kgf__

__Weight of the solid in water = 0.075 kgf Calculate: (a) the apparent loss in weight of solid in liquid (b) the apparent loss in weight of solid in water__

__14. Two children are at opposite ends of an aluminium rod. One strikes the end of the rod with a stone. Find the ratio of times taken by the sound wave in air and in aluminium to reach the second child.__

__15. What is the consequence of two sound waves which arrive at the ear in a time interval shorter than 0.1 s?__

__16. Two bodies of masses m1 and m2 (m1>m2) have same kinetic energy. They are stopped by applying same retarding force. Which body will stop first?__

^{2}=1/2 m2(u2)

^{2}Þ m1(u1)

^{2 }= m2(u2)

^{2 }Þ

^{ }[u1/u2]

^{2}= m2/m1----(ii)

__17. Explain the following: (a) Swimmers are provided with an inflated rubber jacket/tube. Why?__

__(b) It is easier to swim in sea water than in river water. Why?__

__18. A ship sends out ultrasound produced by transmitter that returns from the sea bed and detected after 3.42 s. If the speed of ultrasound waves through sea water is 1530 m/s, what is the distance of the sea bed from the ship?__

*vt/2 =[*1530x3.42]÷2= 2616.3 m

__19. (a) What is the amount of work done: (i) By an electron revolving in a circular orbit of radius r round a nucleus? (ii) By an electron moving with half the speed of light in empty space free of all forces?__

__20. (a)An electric pump is used to pump water from an underground sump to the overhead tank situated 20 m above. It transfers 2000 kg of water to overhead tank in 15 minutes. Calculate the power of pump.__

__(b) What do you mean by instantaneous power of a device?__

__21. If the kinetic energy of the body is increased by 300% then determine the percentage increase in the momentum.__

^{2 }Þ2mE=m

^{2}v

^{2}Þp=Ö2mE

__22. A stone of mass 2 kg is falling from rest from the top of a steep hill. What will be its kinetic energy after 5 s?__

^{2}= 1/2 x 2 x( 49)2 = 2401 J

__23. (a) Explain the work done by the person in the following conditions. (i) When he is standing at a place holding a suitcase in his hand.(ii) When he is moving holding the suitcase in his hands.__

^{o }.·. W = F x s cosq = F x s. cos 90

^{o}= 0 Hence work done on the suitcase is Zero.

__24. Describe the law of conservation of energy by giving two examples__

__25. A compound was found to have the following percentage composition by mass Zn = 22.65%, S = 11.15%, H = 4.88%, O = 61.32%. The relative molecular mass is 287g/mol. Find the molecular formula of the compound, assuming that all the hydrogen in the compound is present in water of crystallizations.__

_{11}H

_{14}

_{11}H

_{14})

_{n }RMM for the molecular = n [65 + 32 + (11x16) +14]= 287n

_{11}H

_{14}

__26. A source of sound produces 20 compressions and 20 rarefactions in 0.2 sec. The distance between a compression and the next (consecutive) rarefaction is 50 cm. find the wavelength, frequency and time period of wave.__

__27. A flask contains 4.4gm of CO__

_{2}calculate (a) How many moles of CO_{2}gas does it contains__(b) How many molecules of CO__

_{2}gas are present it contain? (c) How many atoms of oxygen and C are present in given sample?_{2 }=12+2x16=44gm

_{2}gas = 1 mole

_{2}gas = (1/44)x4.4=0.1 mole

_{2}gas= 6.023x10

^{23}molecules

_{2}gas= (6.023x10

^{23}÷ 44)x 4.4 molecules= 6.023x10

^{22}

_{2 }) = 6.023x10

^{22}x 2 = 1.204x10

^{23 }atoms

_{2 }) = 6.023x10

^{22}x 1 = 6.023x10

^{22}

__28. A mass of 4 kg is dropped from a tower of height 45 m. Calculate__

(i) the potential energy possessed by the body when it is at the top of the tower (ii) the kinetic energy possessed by the body when it is at a height of 35 m (iii) the kinetic energy just before hitting the ground (iv) the velocity of the body just before hitting the ground.

(i) the potential energy possessed by the body when it is at the top of the tower (ii) the kinetic energy possessed by the body when it is at a height of 35 m (iii) the kinetic energy just before hitting the ground (iv) the velocity of the body just before hitting the ground.

^{2}

i) Potential energy possessed by the body when it is at a height of 45 m above the ground

^{2}-u

^{2}=2gS, and substituting value u = 0m/s S= 45-35=10m We get V

^{2 }=196m

^{2}/s

^{2 }KE = 1/2 x 4 x196 = 392 Joule

iii) According to the law of conservation of energy the kinetic energy of the body just before hitting the ground is equal to potential energy of the body at a height of 45m above the ground.Kinetic energy of the body just before hitting the ground = 1764 J

^{2 }Þ v= Ö882 = 29.69 m/s

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## 3 comments:

A helpful guide for students as same as the students need thanks for shearing 9th class sample paper

Its easy to learn things in form of facts and figures.Thanks for sharing these facts.

Molecular Orbital Theory

it was very helpful and easy thank u sir

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