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. April 2016

Rotational Motion

Dffraction

Q1- A cell phone broadcasts 800 MHz signal. If it is operated from the space between two massive radio-wave absorbing buildings with 15 m space between them, what is the angular width of the electromagnetic wave after it emerges from between the buildings?

Q2- How far behind the pinhole should the …

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WPE

On request - Mandy

Q- A bungee jumper of mass m is attached to one end of an elastic rope of length L and force constant k. The other end is fixed to a high bridge. The jumper steps off the bridge and falls from rest. If he just reaches the surface of river before going up again find

(a) The heigh…

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Intereference and diffraction of light

Q1- Light of wavelength 589 nm from a sodium lamp illuminates two narrow slits. The fringe spacing on a screen 150 cm behind the slits is 4.0 mm. What is the spacing between the two slits? 

Q2- A double-slit experiment is performed with light of wavelength 600 nm. The bright interference fringes a…

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Waves-Beats

On request - Karthic

Q- Two strings are adjusted to vibrate at exactly 200 Hz and then the tension in one string is increase slightly. Three beats per second are heard now when the strings are vibrated simultaneously. What is the new frequency of the string that was tightened?

Solution:

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Resitance and Resistivity

Q- An aluminum rod has a resistance of 1.234 Ohm at 20.0°C. Calculate the resistance of the rod at 120°C by accounting for the changes in both the resistivity and its dimensions. (Resistivity of aluminum at 200C is 2.75*10-8 Ohm.m, temperature coefficient of resistivity is 4.4*10-3/0C and the coef…

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Friction-NLM

On request - Kamal

Q- A truck weighing 1 tonne rests on a slope of 30 degrees with its brakes locked. Due to rain the coefficient of friction between the tires and road reduces to 0.3 and the truck starts sliding down the slop under its own weight. What is the net acceleration of the truck down the…

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Current Electricity

Gas Laws And Fluid pressure

Q- Air is trapped in the lower part of a thin tube that stands vertically with 8cm of mercury in the middle with 12 cm of air trapped below it. The top is open and the system is at equilibrium. What will be the length of the trapped air column if the tube is now tilted so that it makes an angle of 6…

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Electric Field and Flux

Q- A non uniform electric field is given by the expression E = ayi + bzj + cxk, where a, b, and c are constants. Determine the electric flux through a rectangular surface in the xy plane, extending from x = 0 to x = w and from y=0 to y=h.

Solution:

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Pulley System

 

Solution:

 

Coulomb's Law

Q- Two point charges q1 = (+) 1µC and q2 = (+) 9µC are separated by a distance of 50cm.

(a) Find the magnitude and direction of the Coulomb force on each charge due to the other.

(b) At what point on the line joining the two charges should a charge q = (-) 1µC be placed so that the net force on …

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Projectile Motion

Q- A builder throws tiles weighing 1.5 Kg horizontally at a speed of 1m/s from a roof 30m high

(a) How far away from the house will the tiles land?

(b) What is the speed of a tile as it hits the ground?

(c) What is the kinetic energy of the tile at ground level?

Solution:

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Drift Speed

(On request- Sunanda)

Q- An aluminum wire having a cross-sectional area of 6.00*10-6 m2 carries a current of 3.70 A. Find the drift-speed of the electrons in the wire. The density of aluminum is 2.70 g/cm3. Assume that one conduction electron is supplied by each atom.

Solution:

 

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Force-Moments

Q- A timber plank 6m long and mass 50 kg is supported horizontally by two posts 1m from each end. A mass of 150 kg is placed on the plank 1m inside of the left hand supporting post. What is the force in each of the two supports?

Solution:

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Coulomb's Law

Q- In the figure q1 = 4µC, q2 = -3µC and q3 =q4= -2µC.

a. What is the magnitude of force exerted on charge q1 by charge q2?

b. What is the magnitude of force exerted on charge q1 by charge q3?

c. What is the horizontal component of force exerted on q1 by q3?

d. What is the resultant force e…

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Hubble law

Q- The tenth brightest member of the cluster of galaxies known as 'Abell1185' has a brightness of 2.70*1010 Wm-2. A line in its spectrum at a wavelength of 503.1 nm is identified as being a member of the Balmer series that has a rest wavelength of 486.1 nm. Consider the luminosity of the tenth brigh…

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Electric Field

A half-ring with a radius 9 cm has a total charge 10 µC uniformly distributed along its length.

(a) What is the linear charge density on the ring?

(b) What is the magnitude of the electric field at the center of the half-ring?

Solutions:

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Doppler's Effect

Q- Joan goes skydiving. As she is falling at terminal velocity, she screams very loudly with a frequency of 1500 Hz. If her friend on the ground directly below her measures the frequency of her scream to be 2000 Hz, how fast is she falling? She hears the echo of her scream as it bounces off the grou…

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WPE

(Requested by Marie)

Q-1 The length of the uncompressed spring is 11.0 cm. The diameter of the wire used to make the spring has been measured using a micrometer screw gauge and has a value of 1.60 mm. The spring has twelve complete turns. When the spring is compressed, the coils are all touching. C…

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