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Physicshelpline

. February 2016

Magnetic Effects

Q- Suppose that you create a magnetic field via two coils of copper wire, each with N turns and each with a current I. The two coils are spaced a distance D apart. Each coil has a radius of R. In the center of the apparatus, create a beam of electrons (each electron has a charge e) accelerated by vo…

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Friction

Q1- A block of mass 5.00 kg is pushed up against a wall by a force F that makes a 60.0° angle with the horizontal. The coefficient of static friction between the block and the wall is 0.30. Determine the possible value(s) for the magnitude of F that allow the block to remain stationary.

Q2- A re…

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C-R Circuit

Q- Three capacitors of capacitance C and a resistor R are connected in series. The combination is connected a battery of EMF V and a switch. Initially the capacitors are uncharged. At t = 0 the switch is closed.

a) What is the charge that accumulates on the plate connected to the positive terminal …

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Angular momentum

Q- A small block of mass 0.91 kg slides without friction on a horizontal table. Initially it moves in a circle of radius r0 = 0.63 m with a speed 1.5 m/s. It is held in its path by a string that passes through a small hole at the center of the circle. The string is then pulled down a distance of r0

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LC Oscillations

Q- A circuit contains a loop with an inductor and a capacitor which and produces an oscillating current. In this LC circuit, L = 3.5 mH and C = 2.6*10-6 F. At t = 0 the charge on the capacitor is zero and the current in the circuit is 1 A.

(a)What is the maximum charge Q that will appear on the cap…

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Momentum-Energy

Q- A car with a mass of mcar = 2080 kg moving towards east and a truck with mass mtruck = 8990 kg moving towards north with velocity vtruck = 8 m/s, enter an intersection. When the two collide they stick together and slide at an angle of 300 north of east.

a) What is the speed of the pair after the…

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Magnetic Field

Q- The current density in a cylindrical wire varies with the distance from its axis r, as j = j0 (r/a). Hear j0 is a constant and ‘a’ is the radius of the wire. Find

(a) Magnetic field at the axis of the wire

(b) Magnetic field at distance r from the axis of the wire.

(c) Magnetic field at th…

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WPE

Q- A railroad hopper car weighs 50000 kg when empty and contains 50000 kg of coal. As it coasts along the track at 9 m/s the hopper opens and steadily releases all the coal onto a platform below the rails over a period of 6 s.

a) How fast does the car travel after all the coal is dumped?

b) What w…

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Electric Potential

Q- Two point charges Q1 and Q2 are placed at a distance d apart.

(a) What is the force acting on each of the charge?  

(b) Derive an expression for electric potential at any point in the space in terms of its coordinates. Consider potential to be zero at infinity. Consider Q1 is at origin and Q2

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Vertical Circle

Q- A small block of mass m slides on a loop the loop track of radius r without friction.

(a) Determine the minimum release height h so that the block completes the loop.

If the actual height of the release is 2h, calculate

(b) The normal force on the block by the track at the lowest point of the…

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WPE

Q- Consider two ideal springs. The spring on the left (constant = 50 N/m) has its left end attached to a fixed wall while its right end is free to move. The spring on the right (constant = 72 N/m) has its right end attached to a fixed wall while its left end is free to move. A block of mass m = 2 kg…

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Coulomb's law and field

Q1- Three charges q1= +10*10-6 C, q2 = -5*10-6 C and q3 = +20*10-6 C are placed in a straight line as bellow.

•        2cm                •                3cm                  •                                                             …

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Electric current

Q1- During the time interval between t = 0 and t = 17 s, the total charge that crossed a plane across a wire at time t is given by (16C)(1-e-t/5.8s)where t is in seconds. What is the maximum value of the current? What is the current at t = 5.8 s?

Q2- A tube of mercury with a resistivity of 9.84 x…

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Rotetional Motion

Q- A uniform square lamina ABCD of mass m and side 2a is free to rotate about a horizontal axis thru A. The axis is perpendicular to the plane of lamina. The lamina is in equilibrium with C vertically below A when it is given an angular speed 2(g/a)^1/2 show that the lamina will perform complete rev…

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Diffraction

Q1- A 1.0 cm wide diffraction grating has 1000 slits. It is illuminated by light of wavelength 550 nm. What are the angles of the first two diffraction maxima?

Q2- A helium-neon laser of wavelength 633 nm illuminates a diffraction grating. The distance between the two first order bright fringes is …

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Sound waves (Doppler Effect)

Q1- Two loudspeakers emit 430 Hz notes. One speaker sits on the ground. The other speaker is in the back of a pickup truck. You hear 9 beats per second as the truck drives away from you. What is the truck's speed?

Q2- A balloon driven by a 35 km/h wind emits a sound of 860 Hz as it approaches a tal…

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Calorimetry

Q1- Ice initially at -7.0°C is mixed with 200 g of water that is initially at 45°C. All of the ice melts and the temperature of the final mixture is 15°C. Find the mass of the ice. Useful info: density of water: 1,000 kg/m3, density of ice: 917 kg/m3, specific heat of water: 1.00 cal/(°C•g), specifi…

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Projectile Motion

Q- A hunter in the plains of Africa is equipped with a bow and arrow. The maximum range of the bow is 100 m. If a Lion charges straight towards him at 30 km/hr and the hunter aims his bow at 300 relative to the horizontal, find

  1. Time of flight of the arrow
  2. Arrow velocity
  3. How far away should the …

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Capacitors

Q1- An electric dipole with a dipole moment of 2x10-29 Cm is positioned in an electric field of 5x105 N/C. If the dipole is perpendicular to the field direction calculate the torque experienced by the dipole.

Q2- Two vertical parallel plate electrodes are placed in a container as a liquid-level det…

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SHM

A uniform cylinder of mass m is rotated through a small angle from the equilibrium position and released. The stiffness of the spring fixed to the cylinder is k. The radius of the cylinder is r. The spring is connected at a distance a from the center of the cylinder. The cylinder rolls without slipp…

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