When tall buildings are constructed on earth, the duration of day night slightly increases. Is it true?

A vibrating string of certain length l under a tension T resonates with a mode corresponding to the first overtone (third harmonic ) of an air column of length 75 cm inside a tube closed at one end. The string also generates 4 beats//s with a tuning fork of frequency n . Now when the tension of the string is slightly increased the number of beats reduces to 2 per second. Assuming the velocity of sound in air to 340 m//s , the frequency n the tuning fork in H_(Z) is (a) 344 (b) 336 (c ) 117.3 (d) 109.3

A tuning fork of known frequency 256 Hz makes 5 beats per second with the vibrating string of a piano. The beat frequency decreases to 2 beats per second when the tension in the piano string is slightly increased. The frequency of the piano string before increasing the tension was

A 1.5m tall boy is standing at some distance from a 30m tall building. The angle of elevation from his eyes to the top of the building increase from 30^(@) " to " 60^(@) as he walks towards the building. Find the distance he walked towards the building.

A tuning fork of frequency 512 Hz makes 4 beats per second with the vibrating string of a piano. The beat frequency decreases to 2 beats per sec. when the tension in the piano string is slightly increased. The frequency of the piano string before increasing the tension was

Two sitar wires A and B producing the note "Dha" are slightly out of tune and produce 5 beats per second. When the tension in the wire B is slighly increased, the beat frequency decreases to 3 Hz. If frequency of A is 512 Hz, what should be original and final frequency of B ?

On a hot summer night, the refractive index of air is smallest near the ground and increases with height from the ground. When a light beam is directed horizontally, the Huygens. principle leads us to conclude that as it travels, the light beam 1......

Find out the increases in moment of inertia I of a uniform rod (coefficient of linear expansion alpha ) about its perpendicular bisector when its temperature is slightly increased by DeltaT .

An electrochemical cell is constructed with an open switch as shown below: when the switch is closed, mass of tin-electrode increases. If E^(@) (Sn^(2+)//Sn) = 0.14V and for E^(@) (X^(n+)//X) =- 0.78V and initial emf of the cell is 0.65V , determine n and indicate the direction of electron flow in the external circuit.

The rotation of the earth having radius R about its axis speeds upto a value such that a man at latitude angle 60^(@) feels weightless. The duration of the day in such case will be

(i) A poor emitter has a large reflectivity . Explain why. (ii) A copper tumbler feels much colder than a wooden block on a cold day. Explain why. (iii) The earth would become so cold that life is not possible on it in the absence of the atmosphere. Explain why? (iv) Why clear nights are cooler than cloudy nights? Why does a piece of red glass when heated and taken out glow with green light? (vi) Why does the earth not become as hot as the sun although it has been receiving heat from the sun for ages? (vii) Animals curl into a ball when they are very cool. Why? (viii) Heat is generated continuously in an electric heater but its temperature becomes constant after some time. Explain why? (ix) A piece of paper wrapped tightly on a wooden rod is observed to get charred quickly when held over a flame as compared to a similar piece of paper when wrapped on a brass rod. Explain why? (x) Liquid in a metallic pot boils quickly whose base is made black and rough than in a pot whose base is highly polished . Why?