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In the arrangement shown in fig. the ends p and q of an unstretchable string move downwards with a uniform speed u. pulleys a and b are fixed. mass m moves upwards with a speed of

Let the speed of the block of mass M is V. The point on the thread just connected to mass M will have the same velocity. The component of... View Article

The apparent frequency of the whistle of an engine changes in the ratio 9 8 as the engine passes a stationary observer. if the velocity of sound is 340 m/s, then the velocity of engine is

Answer: 20 m/s The Doppler effect is the change in the frequency of a wave observed by an observer who is moving relative to the wave source.... View Article

In an oscillating L-C circuit, the maximum charge on the capacitor is Q . The charge on the capacitor, when the energy is stored equally between the electric and magnetic field is.

Here, the given charge on the capacitor is Q. The meaning of the charge on a capacitor, when the energy is stored equally between the electric... View Article

Position-time graph for a particle is shown in the figure. Starting from t=0, at what time t, the average velocity is zero?

We need to discover a point where total displacement equals zero in order to find the time instant when average velocity equals zero. If we look... View Article

in young’s double slit experiment, fringe width observed is β. if the frequency of the source is tripled, then new fringe width will become

The formula that relates the fringe width with the wavelength of the source is given as, ⇒β=λD/d So, we can notice that keeping the distance... View Article

A force of 5 n gives a mass m1 an acceleration of 10 m s–2 and a mass m2 an acceleration of 20 m s-2 . what acceleration would it give if both the masses were tied together?

If we consider that m1 is the mass of the first object and a1 is the acceleration due to the application of an external force of 5N, from... View Article

The north pole of a bar magnet is rapidly introduced into a solenoid at one end (say a). which of the following statements correctly depicts the phenomenon taking placea) No induced emf is developed b) The end A of the solenoid behave as south pole c) The end A of the solenoid behave as north pole d) The end A of the solenoid acquires positive potential

Answer:(c) It happens in accordance with the Lenzs law. The end A becomes north pole, to oppose the motion of the magnet. Lenz’s law states... View Article

when a copper sphere is heated, maximum percentage change will be observed in (1) radius (2) area (3) volume (4) none of these

Answer: (3) volume Change in radius =rΔr=X Change in area =Δ(4πr2/(4πr2) =Δr2/r2 = 2Δr/r =2X Change in Volume =Δ(4/3πr3/(4/3πr3)... View Article

The energy required to break one mole of Cl−Cl bonds in the Cl2 is 242 KJ mol−1 . The longest wavelength of light capable of breaking a single Cl−Cl bond is:

The amount of energy necessary to break a chemical bond between A and B AB is known as bond dissociation energy. The amount of the bond... View Article

A block of mass 2 kg is placed on the floor (μ = 0.4). a horizontal force of 7 n is applied on the block. the force of friction between the block and floor is

The mass of the block as given in the question is 2kg. The coefficient of static friction is 0.4. Force applied on the block is Fnet = 2.8N... View Article

Three charges q, q and q are placed at the vertices of an equilateral triangle of side l as shown in the figure. if the net electrostatic energy of the system is zero, then q is equal to

Electric potential energy is possessed by an object by the virtue of two elements, those being, the charge possessed by an object itself and the... View Article

Consider a uniform square plate of side a and mass m. The moment of inertia of this plate about an axis perpendicular to its plane and passing through one of its corner is:

We can easily find R using the Pythagoras theorem, ⇒R=√ a2−(a/2)2 =a√2 We know that for a square plate, the moment of inertia along a... View Article

The value of acceleration due to gravity ′g′, at earth’s surface is 10m/s2. Its value at the centre of the earth which is assumed to be sphere of radius ′R′ and uniform mass density, is

There is no mass at exact center of Earth to provide a gravitational pull and thus a gravitational acceleration⇒acceleration due to gravity GM/r2... View Article

A proton, a deuteron and an α-particle are projected perpendicular to the direction of a uniform magnetic field with same kinetic energy. The ratio of the radii of the circular paths described by them is

Radius of circular path r = mv/Bq Using p = mv = √2mK where K is the kinetic energy of the particle. We get r = √2mK/Bq ⟹ r ∝ √m/q Given :... View Article

Friction does not depend on the nature of the surface in contact.

The frictional force works to inhibit relative motion between two surfaces when they are in contact. The body can move relative to the surface... View Article

Let ar and at represent radial and tangential acceleration . the motion of particle may be circular if : ( assume that only momentary rest is allowed) A. ar = at = 0 B. ar = 0 and at≠0 C. ar ≠ 0 and at=0 D.ar≠ 0 and at≠0

Tangential acceleration is the reason of a particle travelling faster or slower in a circular motion. A uniform motion is one in which the... View Article

Two circular, similar, coaxial loops carry equal currents in the same direction. If the loops are brought nearer, what will happen?

Answer: Current will decrease in each loop The flux between the two loops rises as they are brought closer. According to Lenz's law, a... View Article

The displacement of a particle is given by x=(t−2)2 where x is in metres and t is in seconds. The distance covered by the particle in first 4 seconds is

The distance travelled is given by x=(t−2)2 = t2–4t+4 As velocity is given by v = dx/dt v=2t−4 Distance covered=∫∣v∣dt =∣t2–4t∣ =4t−t2 for... View Article

A body revolves with constant speed v in a circular path of radius r . the magnitude of its average acceleration during motion between two points in diametrically opposite direction is:

The acceleration will change as there is change in the velocity at any direction.Speed of the body is given to be constant. At diametrically... View Article

A charge q is placed at every corner of a square having side a. how much charge must be placed at its centre to bring the system in equilibrium?

Let the side length of the square be a. In △ACD, ⇒AD2 + CD2 = AC2 ⇒ a2 + a2 =AC2 (AC=√2a) However, OC = AC/2 = a/√2 Because of the... View Article

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