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Physicshelpline

. June 2017

Interference of Light

Q- Light of wavelength λ = 450 nm illuminates two slits. Slit A has a larger opening than slit B. The center of slit A is at y = 0, and the center of slit B is at y = d = 0.1 cm. The screen is L = 1 m away from the plane of the slits. When slit A is open and slit B is closed, the light intensity on…

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Torque, Lever

Q- A fulcrum is created by balancing a ruler on a pencil in the middle. Six one rupee coins are placed at 10 cm to the left of the pivot point.

(a) what is the torque exerted by the stack of the six coins about the pivot point if each coin has a mass of 10 grams?

(b) if the ruler is to be balanced…

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Waves on string

Q- An apparatus similar to the one used in lab uses an oscillating motor at one end to vibrate a long rope with frequency f = 35 Hz and amplitude A = 0.25 m. The rope is held at constant tension by hanging a mass on the other end. The length of the rope is adjusted to form loops.The rope has mass de…

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Work Done

Q- A block of mass 2.50-kg is pushed 2.20 m along a frictionless horizontal table by a constant 16.0-N force directed 300 below the horizontal. Determine the work done by (a) the applied force, (b) the normal force exerted by the table, (c) the force of gravity, and (d) the net force on the block.

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Current Electricity

Q1- A light-bulb designed to operate in a 120.0 V circuit has a resistance of 192 ohms. At what rate does the bulb use electric energy? 

Q2- What is the monthly energy cost of leaving a 60 W bulb on continuously if electricity costs Rs 3.0 per kWh?

Solution:

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Projectile Motion

Q- A projectile is fired form the edge of a 100 meter tall building with an initial speed of 10 m/s at 30 degrees above the horizon and lands on the ground. Neglecting the air resistance. 

(a) Find the horizontal and vertical components of the initial velocity of the projectile.

(b) How long doe…

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Electromagnetic Induction: Solenoid

Q- A solenoid has length L = 30 cm, radius 6 cm, and N1 = 5500 turns; its axis coincides with the z-axis. A circular conducting loop containing N2 = 15 turns of radius a = 3 cm is centered inside the solenoid; the plane of the loop makes a 30° angle with respect to the z-axis. The loop has a net res…

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Newton's Law: Vectors

Q- Three astronauts, propelled by jet backpacks, push and guide a 195 kg asteroid toward a processing dock. One astronaut exerts a force of 30 N, 300 from positive x-axis towards positive y direction, second exerts a force of 55 N along the x-axis and third astronaut exerts a force of 41 N, 600 from…

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Electromagnetic Waves

Q- A vertically polarized radio wave of frequency 9.0*105 Hz traveling into the page. The maximum electric field strength is 1250 V/m. 

(a) What is the maximum magnetic field strength?

(b) What is the magnetic field strength and direction at a point where electric field is E = 625 V/m, downward? …

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Gravitation

Q- Sketch graphs of total mechanical, potential and kinetic energy verses time, on the same paper, for  

(a)  a 0.5 kg metal ball dropped from rest falling from point A to B in 5 second under gravity. (g = 10 m/s2)  

(b) a 5.0g sheet of paper falling with terminal velocity 1 m/s from point A …

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Circular Motion

Q- A cat rides a merry-to-round turning in circular motion with uniform speed. At time t1 = 2.00 s, the cat’s velocity (in m/s) is V1=3.0 i + 4.0 j, measured on a horizontal x-y coordinate system. At t2 = 5.00 s its velocity is V2= (-3.0) i + (-4.0) j. What are the

(a) magnitude of the cat’s ce…

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Conduction Of Heat

Q- A glass windowpane has an area of 3.00 m2 and a thickness of 0.600 cm. If the temperature difference between its faces is 25.0 degrees Celsius, what is the rate of energy transfer by conduction through the window? (coefficient of conductivity for glass to be taken as 0.8 W/(m.K)

Solution:

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Transformers

Q1- A step-up transformer has a primary coil with 100 loops and a secondary coil with 1,500 loops. If the primary coil is supplied with a household current of 120 V and 15 A,

(a) what voltage is produced in the secondary circuit?

(b) What current flows in the secondary circuit?

Q2- The step-down …

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Archimedes Principle

Q- The gravitational force exerted on a solid object is 5.00N. When the object is suspended from a spring scale and submerged in water, the scale reads 3.50N. Find the density of the object. 

Solution:

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Magnetic Field: Coaxial Cable.

Q- An infinite cylindrical conductor of radius a = 1 cm carries a current I1 = 0.3 A out of the page. A coaxial, infinite, thin cylindrical conducting shell of radius b = 5 cm carries a current I2 = 0.12 A, into the page. The current densities in each conductor are uniform.

(a) Calculate the magnit…

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Newton's Law: Variable Mass

Q - A spherical raindrop of radius a, falls from rest under gravity. It falls through a stationary cloud such that because of condensation its radius increases with time at a constant rate k. Find the distance fallen by the raindrop as a function of time t.

Solution:

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Magnetic Field: Torus

Q- A circular torus has inner radius R1 = 30 cm, outer radius R2 = 50 cm, and N = 710 turns wound uniformly around it. The current in the windings is I = 3 A.

(a) Calculate the magnitude of the magnetic field B, inside the torus, in the symmetrical plane along the inner and outer diameter, at the f…

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Rotational Simple Harmonic Motion.

Q- A very light rigid rod with a length of 0.500m extends straight out from one end of a meter-stick. The meter-stick is suspended from a pivot at the far end of the rod and is set into oscillation in a vertical plane. Determine the period of oscillation.

Solution:

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Electromagnetism

Q- A wire frame in the shape of an equilateral triangle of side d = 8 cm, carries current i = 0.25 A. This frame is located in a region of space that contains a constant magnetic field of magnitude B = 1.3 T, Normal to the plane of the frame and the frame is in stable equilibrium. What is the work y…

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Radiation: Stefan Law

Q- The surface of the sun has a temperature of about 5800K. The radius of the Sun is 6.96 X 108 m. Calculate the total energy radiated by the sun each second. Assume the emissivity is 0.986.

Solution:

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