Topper Maths, Science Experts Answer YOUR Queries!

Posted On: March 31, 2009 11:10 am

Your exams are over and a new academic session has begun! So, Topper helps you gear up by answering ALL your queries, within 72 hours!

Here are four questions asked by Topper readers from Class IX, and the answers by Topper maths and science experts.

Subject: Chemistry

Q. Calculate the number of atoms in 0.07g of nitrogen gas.

Posted by: Iona Dias

A. 1 mole of N₂ gas contains 2 x 6.023 x 10²³ atoms of N because N₂ gas is a diatomic molecule. 1 molecule of N₂ gas is made up of 2 atoms of N

For 0.07 g of N₂ gas, number of moles =0.07/28=2.5 x 10^-3

If 1 mole of N₂ gas contains 2.5 x 10^-3 atoms of N 

Therefore 2.5 x 10^-3 mol of N₂ gas contains 2.5 x 10^-3 x 2 x 6.023 x 10²³ =3.011x 10²¹  atoms of N.

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Subject: Physics

Q. The distance b/w Delhi and Agra is 200 m. A train travels the first 100 km at a speed of 50 km/hr. How fast must the train travel the next 100 km, so as to average 70 km/hr for the whole journey?

Posted by: JSharma

A. The average speed = total distance / total time
     The average speed required = 70km/hr

     Total distance = 200 km

     Speed of the train for the first 100 km = 50 km/hr 
     Time taken= 100/50 = 2 hours

      Let the speed for the next 100 km be x km/hr

     Time taken = 100/x
     The total time taken = 2 +100 / x

     Hence 70 = 200 / [ 2+100/x]
     2+ 100/x = 20/7
     x = 116.67 km/hr

     Hence, the train must move with a speed of 116.67 km/hr.

Subject: Biology

Q. What would happen to the cell if the golgi apparatus was not there?

Posted by: Ginny_pretty

A. The cell functioning would be greatly affected if golgi body is absent.

1. The storage, modification and packaging of substances manufactured in the cell will not take place in absence of golgi body. 

2. Lack of vesicles would inhibit the ability of proteins to move from one organelle to the next. As a result the proper modifications of proteins will not occur.

3. Lysosome formation would also be inhibited if golgi apparatus is absent. In addition, formation of complex sugars from simple sugars will not take place.

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Subject: Mathematics

Q. Arrange in ascending order: 4th root of 10, 6th root of 3, 12th root of 216

Posted by: Ashwinivg

A. Take LCM of 4,6 and 12

     LCM = 24

    4^th root of 10 = 24^th root of 10⁶ = 24^th root of 1000000

    6^th root of 3= 24^th root of 3⁴ = 24^th root of 81

    12^th root of 216 = 24^th root of 216² = 24^th root of 46656

    In ascending order we have:

    24^th root of 81< 24^th root of 46656<24^th root of 1000000.

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