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In a Carnot engine efficiency is 40% at hot reservoir temperature T.For efficiency 50%, what will be the temperature of hot reservoir?

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One quarter sector is cut from a uniform circular disc of radius R. This sector has mass M. It is made to rotate about a line perpendicular to its plane and passing through the centre of the original disc. Its moment of inertia about the axis of rotation is

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    For complete disc with mass '4M', M.I. about given axis = (4M)(R2/2) = 2 MR2

    Hence, by symmetry, for the given quarter of the disc

    M.I. = 2 MR2/4 = 1⁄2 MR2

A and B are two metals with threshold frequencies 1.8 × 1014Hz and 2.2 × 1014Hz.Two identical photons of energy 0.825 eV each are incident on them. Then photoelectrons are emitted in (Take h = 6.6 × 10–34Js)

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A motor of 100 H.P. moves a load with a uniform speed of 72 km/hr. The forward thrust applied by the engine on the caris

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    Forward thrust, F=\(\frac{p}{v}=\frac{100\times 746}{20}=3730\: N.\)

A uniform wire of length 20 m and weighing 5 kg hangs vertically.If g = 10 m/s2, then the speed of transverse waves in the middle of the wire is

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Two similar coils of radius Rare lying concentrically with their planes at right angles to each other. The currents flowing in them are I and 2 I, respectively. The resultant magnetic field induction at the centre will be

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A particle moves along a circle of radius \(\left ( \frac{20}{\pi } \right )\)m with constant tangential acceleration. It the velocity of particle is 80 m/sec at end of second revolution after motion has begun, the tangential acceleration is

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    Circumference of circle is 2πr = 40m

    Total distance travelled in two revolution is 80m. Initial velocity u =0, final veloctiy v = 80 m/sec

    so from

    v2=u2 + 2as

    ⇒ (80)2 = 02 + 2 × 80 × a

    ⇒ a = 40m/sec2

Fraction of tritium left after 150 years (half life of tritium is 12.5 years) is

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If voltage across a bulb rated 220 Volt-100 Watt drops by 2.5% of its rated value, the percentage of the rated value by which the power would decrease is

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DIRECTIONS: These are Assertion-Reason type questions. Each of these question contains two statements:Statement-1 (Assertion) and Statement-2 (Reason). Answer these questions from the following four options.

Statement-1 Stress is the internal force per unit area of a body.

Statement-2 Rubber is less elastic than steel.

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    (b)Statement-1 is True, Statement -2 is True; Statement-2 is NOT a correct explanation for Statement - 1

    Stress is defined as internal force (restoring force) perunit area of a body. Also, rubber is less elastic than steel, because restoring force is less for rubber than steel.

Two forces are such that the sum of their magnitudes is 18 N and their resultant is 12 N which is perpendicular to the smaller force. Then the magnitudes of the forces are

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Force between two plates of a capacitor is

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The earth is assumed to be sphere of radius R. A platform is arranged at a height R from the surface of Earth.The escape velocity of a body from this platform is kv, where v is its escape velocity from the surface of the earth. The value of k is

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A coin placed on a gramophone record rotating at 33 rpm flies off the record, if it is placed at a distance of more than 16cm from the axis of rotation. If the record is revolving at 66 rpm, the coin will fly off if it is placed at a distance not less than

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Two tones of frequencies n1 and n2 are sounded together.The beats can be heard distinctly when

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    As number of beats/sec = diff. in frequencies has to be less than 10, therefore 0 <(n1–n2) < 10

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