National Science Olympiad Forum By SOF Olympiad Trainer

DRAVIT GUPTA from Mother's Global School, New Delhi

Subject :NSO Class : Class 9

A cavity of radius R/2 is created in a sphere of radius R and mass M at the periphery and this mass is placed at a distance 2R from the centre of the sphere as shown in figure. The force between the two is

A

B

C

D

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Ans 1:

Kshithy G Nair from Chinmaya Vidyalaya Tripunithura, Kochi

Class : Class 9

i think the above explanation is good and would be more accurate if shft of centre of mass is calculated

Ans 2:

Gh from Mahatma, Ghaziabad

Class : Class 10

I think it should be 7GM^2/256R^2 G is constant. M will become 7M/8 due to mass removal .M2 will be M/8 . Distance is 2 R . So the product is equivalent to the above. But I don't know how it is not in answers

Ans 3:

divanshi from sacred heart convent school, barnala

Class : Class 4

this need more details as the question is not clear

Ans 4:

pratham from Indian School Ghubra, Muscat, Muscat

Class : Class 7

I agree with Gh from Mahatma, Ghaziabad, options are not correctly provided in the question.

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DRAVIT GUPTA from Mother's Global School, New Delhi

Subject :NSO Class : Class 9

A hollow cylinder of height 1 m whose both crosssections are closed with a membrane of negligible mass, just floats without sinking in a liquid of density 1.9 × 10³ kg m^-3. If the outer diameter and the density of the cylinder are 1 m and 10⁴ kg m^-3 respectively, then the inner diameter of the cylinder will be

A0.3 m
B0.5 m
C0.8 m
D0.9 m

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Ans 1: (Master Answer)

Admin from revisewise, Noida

Class : Class 1

The correct answer is D.

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DRAVIT GUPTA from Mother's Global School, New Delhi

Subject :NSO Class : Class 9

Two identical satellites SI and SII revolve round the earth in circular orbits at distance R and 3R respectively from the surface of the earth, where R is the radius of the earth. The ratio of linear momenta of SII to SI is

A√3 : 1
B1 : 3
C2 : 1
D1: √2

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Ans 1:

Harsh Gupta from AECS Narora, Narora

Class : Class 9

Ans 2:

Soumyaranjan Nath from Delhi Public School , Angul

Class : Class 9

how

Ans 3:

Harsh Gupta from AECS Narora, Narora

Class : Class 9

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DRAVIT GUPTA from Mother's Global School, New Delhi

Subject :NSO Class : Class 9

Two cylinders of same cross-section and length L but made of two materials of densities ρ1 and ρ2 are cemented together to form a cylinder of length 2L. If the combination floats in water with a length L/2 above the surface of water and ρ1 < ρ2, then

Aρ1 > 1 g cm^–3
Bρ1 > 3/2 g cm^–3
Cρ1 < 8/9 g cm^–3
Dρ1 < 3/4 g cm^–3

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Ans 1:

from kv2, kalpakkam

Class : Class 9

i dont know the answer to this question \

Ans 2:

ashishlal2003 from dps east, bangalore

Class : Class 9

why doesn't anyone answer?

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DRAVIT GUPTA from Mother's Global School, New Delhi

Subject :NSO Class : Class 9

The given diagram shows a barometer.

If the atmospheric pressure is 76 cm Hg, then what is the value of h?

A75 cm Hg
B76 cm Hg
C77 cm Hg
D80 cm Hg

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Ans 1:

Gireesha from innocent hearts school jalandhar, Jalandhar

Class : Class 10

Ans 2:

Aravinda Venkatesan from Gd Goenka school indrapuram, Ghaziabad

Class : Class 9

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Pramath Ram from Canara CBSE, Mangalore

Subject :NSO Class : Class 7

The diagram shows identical lamps X and Y connected in series with a battery. The lamps light with normal brightness. A third lamp Z is connected in parallel with lamp X. What happens to the brightness of lamp Y?

A Brighter than normal
B Normal
C Dimmer than normal
D Very dim (cannot be seen).

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Ans 1:

Aparajita from Mount Litera Zee School, Vasco da gama

Class : Class 8

As it is parallel to x

Ans 2:

Anubhab Maity from Dps ruby park, Kolkata

Class : Class 7

Ans 3:

Jai kumar Bohara from Dps, Udaipur

Class : Class 9

Option is correct if the battery has infinite nergy

Ans 4:

Arnav Raj Sharma from Dpsvk, Gurgaon

Class : Class 9

option b

Ans 5:

Arnav Raj Sharma from Dpsvk, Gurgaon

Class : Class 9

why a. why not b. i think that bulb x will turn dimmer but y will remain the same.

Ans 6:

Aparajita from Mount Litera Zee School, Vasco da gama

Class : Class 8

option D

Ans 7:

Kshitij verma from DPS KAMPTEE NAGPUR, Nagpur

Class : Class 8

brighter than normal as total current through the ckt will increase.

Ans 8:

Taksh from St John High School, Mumbai

Class : Class 8

Ans a

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Pramath Ram from Canara CBSE, Mangalore

Subject :NSO Class : Class 7

A drunkard is walking along a straight road. He takes 5 steps forward and 3 steps backward and so on. Each step is 1 m long and takes 1 s. There is a pit on the road 11 m away from the starting point. The drunkard will fall into the pit after

A 21 s
B 29 s
C 31 s
D 37 s.

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Ans 1:

Aditya kumar from Sapphire International School, Noida

Class : Class 8

Its "b" (sec with steps) (5-3)+(5-3)+(5-3)+5=11 (29 sec)

Ans 2:

Soumyajit Roy from Delhi Public School Jamnagar, Jamnagar

Class : Class 9

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dayalakshmi dinesh from BHAVAN'S MUNSHI VIDYASHRAM, Kochi

Subject :NSO Class : Class 5

If '+' means '÷' '-' means 'x', '÷' means '+' and 'x' means '-', then

36 x 12 + 4 ÷ 6 + 2 - 3 = ?

(A) 2

(B) 18

(C)

(D) 42

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dayalakshmi dinesh from BHAVAN'S MUNSHI VIDYASHRAM, Kochi

Subject :NSO Class : Class 5

After removing some squares from a big square, the following figure is obtained. The length of one side of a small square is 3 cm. Find the area of the figure.

(A) 68 cm²

(B) 603 cm²

(C) 612 cm²

(D) 729 cm²