A sphere of solid material of relative density 9 has a concentric spherical cavity and just sinks in water. If the radius of sphere be R, then the radius of cavity (r) will be related to R as

1. r³ = \({{8}\over{9}}\)R³

^2.r³ = \({{2}\over{3}}\)R³

^3.r³ = \({{\sqrt{8}}\over{3}}\)R³

^4.r³ = \({{\sqrt{2}}\over{3}}\)R³

Subtopic: Archimedes' Principle |

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Q25:

A car is travelling with a linear velocity v on a circular road of radius r. If it is increasing its speed at the rate of a m/s², then the resultant acceleration will be

1.

2.

3.

4.

Subtopic: Circular Motion |

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Q26:

A uniform magnetic field parallel to the plane of paper, exsisted in space initially directed from left to right. When a bar of soft iron is placed in the field parallel to it, the lines of force passing through it will be represented by figure.

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2.

3.

4.

Subtopic: Magnetic Materials |

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Q27:

A body starts from rest and moves with a uniform acceleration. The ratio of the distance covered in the nth second to the distance covered in n second

1.

2.

3.

4.

Subtopic: Uniformly Accelerated Motion |

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Q29:

The current i and voltage V graphs for a given metallic wire at two different temperatures T₁ and T₂ are shown in the figure. It is concluded that

1. T₁>T₂

_2.T₁<T₂

_3.T₁ = T₂

_4.T₁ = 2T₂

Subtopic: Derivation of Ohm's Law |

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Q30:

The internal resistance of primary cell is 4Ω. It generates a current of 0.2 A in an external resistance of 21Ω. The rate at which chemical energy is consumed is providing the current is

1. 0.42 J/s

2. 0.24 J/s

3. 5 J/s

4. 1 J/s

Subtopic: Heating Effects of Current |

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Q31:

There are four point charges +q, -q, +q and –q are places at the corners A, B, C and D respectively of a square of side a. The potential energy of the system is times