A stone is thrown from the top of a building with an initial velocity of 25 m/s straight upward. The building is 47 m high, and the stone just misses the edge of the roof on its way down. Determine:
a. The time needed for the stone to reach it maximum height
b. The maximum height the stone reaches
c. The time needed for the stone to return to the level of the thrower
d. The velocity of the stone at the instant it returns to the level of the thrower
e. The velocity of the stone and position of the stone at t=3 seconds
f. The velocity of the stone just before it hits the ground
g. The total time the stone is in the air
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Consider a GaAs p-n junction diode. The p-type acceptor is Zn, with a dopant concentration of 2 x 10^17 cm^-3 and the n-tpye donor is Si, with a dopant concentration of 5 x 10^16 cm^-3. Working at temp= 300 K.
a) Calculate the Fermi Level in the p-type material. Assume that the hole density is equal to the density of the p-dopant atoms.
b) Performing the same calculation for the n-type material gives a fermi level of 1.363 eV. What is the zero-bias built- in potential at the junction?
c) Calculate the width of the depletion zone for this case
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A block of mass m is connected to a string of negligible mass and slides on a slick surface in a circular path of radius 0.5 meters. The other end of the string passes through a hole in the surface and is connected to an identical block of mass m beneath the surface. All friction may be neglected in this problem and the string's mass and stretch are negligible.
1. Write the Newton's second law expressions for each block and the string with the apporpriate sum of physical forces and expressions for Fnet.
2 The top block is removed so that one block of mass m is in circular mtion with mass 3m pulling on the other end of the string. As the mass of 3m falls, pulling the string, the mass in circular motion speeds up in such a way that the prodcut of the radius and tangential speed remains constant RVtan = R(knot)V(knot)tan from [3]. Find the radius and spped at which the hanging mass reaches equilibrium.
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A circular loop in the plane of the paper lies in a 0.61T magnetic field pointing into the paper.
A) If the loop's diameter changes from 19.6cm to 7.4cm in 0.19s , what is the direction of the induced current? (counterclockwise or clockwise)
B) What is the magnitude of the average induced emf?
C) If the coil resistance is 3.7? , what is the average induced current?
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In Fig.30.11 in the textbook, switch S1 is closed while switch S2 is kept open. The inductance is L = 0.110 H , and the resistance is R = 120 Ω . When the current has reached its final value, the energy stored in the inductor is 0.240 J . What is the emf E of the battery?After the current has reached its final value, S1 is opened and S2 is closed. How much time does it take for the energy stored in the inductor to decrease to a half of the original value?
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Two infinite planar sheets are placed parallel to each other. One sheet is uniformly charged with +10 nC/cm^2 and the other with -20nC/cm^2.
A point charge of -5 nC is placed
a) between the sheets
b) in the outside regions.
For each case calculate the strength and show the direction of the
electric force experienced by the point charge.
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Pool players often pride themselves on their ability to impart a large speed to a pool ball. In the sport of billiards, event organizers often remove one of the rails on a pool table to allow players to measure the speed of their break shots (the opening shot of a game in which the player strikes a ball with his pool cue). With the rail removed, a ball can fly off the table. As the only participant with a physics background, they have placed you in charge of determining the speed of the players\' break shots.
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S = 1/(?0) E X B
How was the poynting vector derived? Please give a detailed derivation of equations that leads to the Poynting Vector.
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Using both math and physics to explain
(a) What is the contrast?
(b) On a clear sky, why you can’t see forever?
© When the aircraft parks on the snow surface, sometime it is hard to know that it is in the air or
on the surface, why?
(d) Why we can see a light very far away during night, but not during daytime?
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In a model AC generator, a 497 turn rectangular coil 14.0 cm by 23 cm rotates at 115 rev/min in a uniform magnetic field of 0.58 T.
(a) What is the maximum emf induced in the coil?
V
(b) What is the instantaneous value of the emf in the coil at
t = (?/39) s? Assume that the emf is zero at
t = 0.
V
(c) What is the smallest value of t for which the emf will
have its maximum value?
s
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A boy pushes his little sister in a sled across the horizontal ground. He pushes down and to the right on the sled at an angle of 35 degrees from the horizontal. The mass of the sled and the sister together is 60 kg. The coefficient of static friction of the sled with the ground is 0.3 and the coefficient of kinetic friction is 0.2. a) Draw a sketch of the situation and a force diagram of the sled, labeling all forces clearly. b) With what force does the boy have to push to start the sled moving from rest? c) If he continues to push with this force after the sled is moving, what will be the sled's acceleration? d) How long will he have to push the sled with this force unitil the it is moving at 2 m/s? e) Discuss whether or not your answers to parts b through d pass the "common sense" test. Be specific about why you think the answers do or do not make sense.
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Rolling Friction questions.
A- How can I quantitatively test Newtons 2nd law for a ball rolling down a wooden ramp using
Ball, wooden ramp, motion sensor, Logger Pro software, computer, meter stick, stopwatch, digital balance, spring scale?
B- How can I determine the coefficient of rolling fiction between the ball and wooden ramp if I lay the ramp flat (no tilt) using the same equipment?
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A silver wire with resistivity 1.59 x 10^-8 ? x m carries a current density of 4.0 mm^2. What is the magnitude of the electric field inside the wire?
A) 0.064 V/m
B) 2.5 V/m
C) 0.040 V/m
D) 0.10 V/m
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design an experiment to measure the effects of chromatic aberration? Just a simple procedure, thanks.
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