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An ac source is rated at 220V, 50Hz. The time taken for voltage to change from its peak value to zero is
A 5000 kg rocket is set for vertical firing. The exhaust speed is 800 m/s. To give an initial upward acceleration of 20 m/s^{2}, amount of gas ejected per second to supply needed thrust will be (g=10 m/s^{2})
The energy of a photon of light with wavelength 5000Å is approximately 2.5eV. This way the energy of an Xray photon with wavelength 1Å would be
Electric field at the centroid of a triangle carrying q charge at each corner is
A particle of mass m is executing uniform circular motion on a path of radius r. If p is the magnitude of its linear momentum. The radial force acting on the particle is
A particle of mass m and charge q is placed at rest in a uniform electric field E and then released. The kinetic energy attained by the particle after moving a distance y is
Two NOT gates are connected at the two inputs of a NAND gate. This combination will behave like
A body is projected at such an angle that the horizontal range is three times the greatest height. The angle of projection is
In the following question, a Statement of Assertion (A) is given followed by a corresponding Reason (R) just below it. Read the Statements carefully and mark the correct answer
Assertion(A):Two bodies 1 and 2 exerting forces on each other.Force exerted on the body 1 by body 2 is F^{ →} 12 and that exerted on the body 2 (by body 1) is F^{ →} 21 . Then F^{ → } 12 = − F^{ → } 21 .
Reason(R):Force F^{ → } 12 is of action and force F ^{→} 21 is of reaction.
Assertion is true as acc to Newton second law Fab=Fba i.e every action has an equal and opposite reaction. Since force is a Vector quantity opposite direction is to be indicated by negative sign. So in question assertion is true but in reason the force of reaction is not in opposite direction because negative sign is not there. So reason is false.
The M.I. of a body about the given axis is 1.2 kg x m^{2} initially the body is at rest. In order to produce a rotational kinetic energy of 1500 joule an angular acceleration of 25 rad/sec^{2 } must be applied about that axis for a duration of
The radionuclide ^{56}Mn is being produced in a cyclotron at a constant rate P by bombarding a manganese target with deutrons. ^{56}Mn has a half life of 2.5 hours and the target contains large number of only the stable manganese isotope ^{55}Mn. The reaction that produces ^{56}Mn is:
^{55}Mn+d→^{56}Mn+P
After being bombarded for a long time, the activity of ^{56}Mn becomes constant equal to 13.86×10s^{−1}. (Use ln2 = 0.693; Avogadro number = 6×10^{23} atomic weight of ^{56}Mn = 56gm/mole)
Q. After a long time bombardment, number of ^{56}Mn nuclei present in the target depends upon
(a) The number of ^{56}Mn nuclei present at the start of the process
(b) Half life of the ^{56}Mn
(c) The constant rate of production P
A circular road of radius 1000 m has banking angle 45º. The maximum safe speed of a car having a mass 2000 kg will be, if the coefficient of friction between tyre and road is 0.5 :
A bob of mass m, suspended by a string of length ℓ_{1} is given a minimum velocity required to complete a full circle in the vertical plane. At the highest point, it collides elastically with another bob of mass m suspended by a string of length ℓ_{2}, which is initially at rest. Both the strings are massless and inextensible. If the second bob, after collision acquires the minimum speed required to complete a full circle in the vertical plane, the ratio ℓ_{1}/ℓ_{2} is.
A ring of radius 2m weights 100 kg. Its having pure rolling motion on a horizontal floor so that its centre of mass has a speed of 20 cm/s. If work done to stop it is xJ. Then x will be
2 kg ice at – 20°C is mixed with 5 kg water at 20°C. Then final amount of water in the mixture would be :
Given specific heat of ice = 0.5cal/g°C, specific heat of water = 1 cal/g°C, Latent heat of fusion of ice = 80 cal/g. (in kg)
A diode having potential difference 0.5 V across its junction which does not depend on current, is connected in series with resistance of 20 Ω across source. If 0.1 A passes through resistance then what is the voltage of the source :
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