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Physicshelpline

. November 2016

Circular Motion

Q- The drive train of a bicycle has wheels 67.3 cm in diameter and pedal cranks 17.5 cm long. The cyclist pedals at a steady cadence of 76.0 rev/min. The chain engages with a front sprocket 15.2 cm in diameter and a rear sprocket 7.00 cm in diameter.

(a) Calculate the speed of a link of the chain r…

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Ray Optics

Q- Two convex lenses are separated by the sum of their focal lengths. The first lens has a focal length of 150cm, while the second has a focal length of 120 cm. If a 10 cm high object is placed 440 cm from the first lens, determine the final image position relative to the 150 cm lens, the final imag…

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Motion in 1 D: Relative velocity

(On request - Ritik)

Q- Two towns A&B are connected by a regular bus service with a bus leaving in either direction every T min. A man cycling with a speed of 20 Km/hr in the direction A to B notices that a bus goes past him every 18min in the direction of his motion, and every 6 min in the opposit…

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Fluids: Viscosity

Q- A patient is to be given a blood transfusion. The blood is to flow through a wide tube from a raised bottle to a needle inserted in the vein. The inside diameter of the 3.8 cm long needle is 0.4 mm and the required flow rate is 4 cm3 of blood per minute. How high should the bottle be placed a…

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Modern Physics: Mass energy relation

Q- The sun radiates electromagnetic energy at a constant rate of 3.92*1026 W.

(a) What is the change in the sun’s mass during each second due to radiating energy?

(b) The mass of the sum is 1.99*1030 kg. What fraction of the sun’s mass is lost during a human lifetime of 75 years?

Solution:

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Friction

(On request - Emily)

Q- A 225 kilogram piano is pushed across the floor with a 155 Newton Force if the piano accelerates at 0.37 m/s2 what is the coefficient of friction between the piano and the floor?

Solution:

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Ray Optics: Total internal reflection

Q- A blue light point source is placed at the bottom of a 15 foot deep swimming pool, filled with a liquid of refractive index 2.3. Determine the area of the blue circular light patch seen on the surface of the liquid.

Solution:

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Simple Harmonic Motion

Q- Astronauts in space cannot weigh themselves by standing on a bathroom scale. Instead, they determine their mass by oscillating on a large spring. Suppose an astronaut attaches one end of a large spring to her belt and the other end to a hook on the wall of the space capsule. A fellow astronaut th…

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AC Circuits: Capacitive Reactance

(a) An 8.0µF capacitor is connected to the terminals of a 60Hz AC source whose rms voltage is 150V. Find the capacitive reactance and rms current in the circuit.

(b) If the frequency is doubled, calculate the new rms current.

Solution:

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Circular Motion

Q- A car accelerates uniformly from rest and reaches a speed 20.0 m/s in 10.0 s. The tires have diameter 60.0 cm and do not slip on the pavement.

(a) Find the number of revolutions each tire makes during this motion.

(b) What is the final angular speed of a tire in revolutions per second? 

Sol…

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Wave Optics: Interference

Q- Light of wavelength 440 nm illuminates two 35 cm glass slides. An object is placed between the ends of the slides causing an air wedge to form between the slides. 445.6 dark fringes per cm are seen on the slides. Determine the thickness of the air wedge.

Solution:

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Projectile Motion

Q- An airplane with a speed of 75 m/s is climbing upward at an angle of 30.0 ° with respect to the horizontal. When the plane's altitude is 600 m, the pilot releases a package.

(a) Calculate the distance along the ground, measured from a point directly beneath the point of release, to where the …

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Electrostatics: Potential and Field

Q- The potential at a point on the axis of a uniformly charged circular disk is given by

          

Where s is the surface charge density, r is the distance of the point from the center of the disk and ‘a’ is the radius of the disk. Find an expression for the electric field as a function…

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Standing Waves: Air column

Q- The normal range of hearing is about 20 to 20000 Hz. Assume that your hearing range is 27 to 18500 Hz. (Use 340 m/s as the speed of sound.)

(a) What is the greatest length of an organ pipe that would have its fundamental note in your hearing range if it is closed at one end?

(b) What is the gre…

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Ray Optics

Q- An object is placed 58 cm from a concave mirror of radius 33 cm.

(a) Find the location of the image.

(b) What is the magnification of the mirror?

Solution:

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Electrostatics: Potential

Q- In moving from point A to point B, an alpha particle lost 9.8*10-17 J of electric potential energy and gains an equal amount of kinetic energy. What is the potential difference between A and B?

Solution:

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Newtons Laws of motion: Friction

Q- An 80 N crate of apples sits at rest on a ramp that runs from the ground to the bed of a truck. The ramp is inclined at 30° to the ground.

(a) What is the normal force exerted on the crate by the ramp?

(b) What is the static frictional force exerted on the crate by the ramp?

(c) What is the m…

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Electromagnetism

Q- A single-turn square loop of wire of side 2.00 cm, carries a clockwise current of 200 A. The loop is inside a solenoid, with the plane of the loop perpendicular to the magnetic field of the solenoid. The solenoid has 30 turns/cm and carries a clockwise current of 15.0 A Find the force on each sid…

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Projectile Motion

Q- A marble is thrown horizontally with a speed of 20 m/s from the top of a building. When it strikes the ground, the marble has a velocity that makes an angle of 37 ° with the horizontal. From what height above the ground was the marble thrown?

Solution:

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Doppler effect: Light waves

Q- A distant galaxy is simultaneously rotating and receding from the earth. As the drawing shows, the galactic center is receding from the earth at a relative speed of uG = 1.8*106 m/s. Relative to the center, the tangential speed is vT = 0.3*106 m/s for locations A and B, which are equidistant from…

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