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Physicshelpline

. September 2018

Heat Radiation

Q- A student is trying to decide what to wear. His bedroom is at 20.0 degrees Celsius. His skin temperature is 35.0 degrees Celsius. The area of his exposed skin is 1.50 m2. People all over the world have skin that is dark in the infrared, with emissivity about 0.900. Find the net energy loss from h…

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Alternating Current: Admittance

Q- For the circuit of Figure

(a) Find the total admittance in polar form.

(b) Draw the admittance diagram.

(c) Find the value of C in microfarads and L in Henries if the current in the circuit is

          I = 3 sin (377 t + 600)

Solution:

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Sound: Intensity and Loudness

Q- When a pin of mass 0.120 g is dropped from a height of 0.80 m and 0.05% of its energy is converted into a sound pulse with a duration of 0.1 s. 

(a) Estimate the range at which the dropped pin can be heard if the minimum audible intensity is 10-11 W/m2.

(b) Your result in (a) is much too larg…

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Collision

Q- A truck was traveling north when, at intersection, collided with a car traveling east. The two vehicles remained joined together after the collision. The skid marks leading from the intersection 20 m at an angle of 30o north of east before stopping. The truck weighed 1200 kg and the car weighed …

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Kirchhoff's Law: Nodal Analysis

Q- Find current through all resistances in the given network.

Solution:

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Rotational Oscillations

Q- Two disks with moments of inertia I1 (top disk) and I2 (bottom disk) are connected by a mass-less torsion spring which produces a restoring torque with magnitude |τ| =  c |θ12| on each disk, where θ1 and θ2 are the angular positions of the disks. (You can imagine that this system is free…

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