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A bullet hits a lock kept at rest on a smooth horizontal surface andgets embedded into it. Which of the following does not change?

(A) a linear momentum of the block

(B) kinetic energy of the block

(C) gravitational potential energy of the block

(D) temperature of the block

(A) a linear momentum of the block

(B) kinetic energy of the block

(C) gravitational potential energy of the block

(D) temperature of the block

Answer: C

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The motor of an engine is erotating about its axis with an angular velocity of 100 rev/minute. It comes to rest in 15 s, after being switched off. Assumgn cnstant angular decelertion, calculate the number of revolutions made by it before coming to rest.

A parallel beam of light of wavelength 560 nm falls on a thin film of oil (refractive index = 1.4). What should be the minimum thickness of the film so that it strongly

S4 T z reflects the light ?

S4 T z reflects the light ?

A Galilean telescope is constructed by an objective of focal length 50 cm and a eyepiece of focal length 5.0 cm a. find the tube length and magnifying power when it is used to see n object at a large distancei normal adjustment b. if the telescope is to focus an object 2.0 m away from the objective what should be the tube length and angular magnification, the image again forming at infinity?

If aperture diameter of the lens of a telescope is 1.25 m and wavelength of light used is 5000 Å its resolving power is （ ）

A. \({2.05}\times{10}^{{{6}}}\)

B. \({2.5}\times{10}^{{{5}}}\)

C. \({4.1}\times{10}^{{{5}}}\)

D. \({4.1}\times{10}^{{{6}}}\)

An electric current of \({0.4}{A}\) is passed through a silver voltameter fro half an hour.Find the amount of silver deposited on the cathode. \({E}{C}{E}\) of silver \(={1.12}\times{10}^{{-{4}}}{k}{g}{C}^{{-{1}}}\)

The coil of an electric bulb takes 40 watts to start glowing. If more than 40 W is supplied, 60% of the extra power is converted into light and the remaining int heat. The bulb consumes 100 W at 220 V. Find the percentage drop in the light intensity at a point if the supply voltage changes from \({220}{V}\to{200}{V}\).

A particle of mass 0.3 kg subject to a force \({F}=-{k}{x}\) with \({k}={15}{N}/{m}\). What will be its initial acceleration if it is released from a point 20cm away from the origin?

(a) \({15}{m}/{s}^{{2}}\)

(b) \({3}{m}/{s}^{{2}}\)

(c) \({10}{m}/{s}^{{2}}\)

(d) \({5}{m}/{s}^{{2}}\)

(a) \({15}{m}/{s}^{{2}}\)

(b) \({3}{m}/{s}^{{2}}\)

(c) \({10}{m}/{s}^{{2}}\)

(d) \({5}{m}/{s}^{{2}}\)

Two particles of mass 1 kg and 3 kg move towards each other under their mutual force of attraction. No other force acts on them. When the relative velocity of approach of the two particles is 2m//s, their centre of mass has a velocity of 0.5 m/s. When the relative velocity of approach becomes 3 m/s. When the relative velocity of approach becomes 3m/s, the velocity of the centre of mass is 0.75 m/s.

The torque \(\tau\) on a body about a given point is found to be equal to A x L, where A is constant vector and L is the angular momentum of the body that point. From this, it follows that

(A) \(\frac{{{d}{L}}}{{{\left.{d}{t}\right.}}}\) is perpendicular to L at all instants of time.

(B) the component of L in the direction of A does not change with time.

(C) the magnitude of L does not change with time.

(D) L does not change with time

(A) \(\frac{{{d}{L}}}{{{\left.{d}{t}\right.}}}\) is perpendicular to L at all instants of time.

(B) the component of L in the direction of A does not change with time.

(C) the magnitude of L does not change with time.

(D) L does not change with time

A thermal power plant produed electric power of 600kW at 4000V, which is to be transported to a place 20 km away form the power plant for consumer's usage. It can be transported either directly with a cable of large current carrying capacity or by sing a combination of step-up and step-down transfprmers at the two ends. THe drawback of the direct transmission is the large energy dissipation. In the method wsing transformers, the dissipatiion is much smaller. In this method a step-up transformers is used at the plant side so that the current is reduced to a smaller value. At the consumers'end, a step-down transformer is used to supply power to the consumers at the specified lower voltage. It is reasonable to assume that the power cable is purely resostive and the transformers are ideal with power factor unity. All the currents and voltagementioned are values.

In the method using the transformers assume that the ratio of the number of turns in the primary to that in the secondary in the step-up transformer is 1:10 if the power to the consumers has to be supplied at 200V, the ratio of the number of turns in the primary to that in the secondary in the step-down transformer is

(A) \({200}:{1}\)

(B) \({150}:{1}\)

(C) \({100}:{1}\)

(D) \({50}:{1}\)

In the method using the transformers assume that the ratio of the number of turns in the primary to that in the secondary in the step-up transformer is 1:10 if the power to the consumers has to be supplied at 200V, the ratio of the number of turns in the primary to that in the secondary in the step-down transformer is

(A) \({200}:{1}\)

(B) \({150}:{1}\)

(C) \({100}:{1}\)

(D) \({50}:{1}\)

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