a. Write an expression for the electric field vector of a uniform plane wave in free space that is propagating in the direction given by a line from the origin to the point (3,0,4) and that is linearly polarized along the y-direction. It has a wavelength of 2 �m and reaches its positive maximum amplitude of 20 V/m at a distance of 1 m from the origin at t = 0 s.

b. Compute the irradiance of this wave.

1. What is the potential at the center of a charged circular loop with a total charge of Q and radius R?
2. A point charge q is moved a distance d parallel to the x-axis in a region of space where there is an electric field of magnitude E which is parallel to the y-axis. What is the change in the potential energy of the charge?
3. A collection of point charges exists in a region of space. Is it possible to arrange the charges so that the potential at a point P is equal to zero?
4. If the potential is constant in a certain region of space, what can you say about the electric field there?

6. In each situation described below, compare the magnitudes of the two forces. Explain your answer in each case.

a. A 90-kg an and a 60-kg boy each have one hand extended out in front and are pushing on each other. Neither is moving. Compare the force exerted by the man’s hand on the boy’s hand to that exerted by the boy’s hand on the man’s.

b. In (a), the boy begins to slide along the floor. Now compare the same two forces between their hands.

c. A person is leaning against a wall with her hand straight out pushing against the wall. Compare the force exerted by her hand on the wall to that exerted by the wall on her hand. What is the type of force exerted by the wall on her hand called?

d. In (c), is the force exerted by the wall on the person’s hand passive or active explain?

e. In (c) compare the horizontal component of the force exerted by the person’s feet on the floor to the horizontal component of the force exerted by the floor on her feet. What is the type of force exerted by the floor on her feet called?

f. Is the force describe in (e) that the person exerts on the floor passive or active? Explain.

Two of the wavelengths emitted by a hydrogen atom are 121.6nm and 1876nm .

What is the m value for the wavelength 121.6nm ?

What is the n value for the wavelength 121.6nm ?

What is the m value for the wavelength 1876nm ?

What is the n value for the wavelength 1876nm ?

For the wavelength 121.6nm , is the light infrared, visible, or ultraviolet?

For the wavelength 1876nm , is the light infrared, visible, or ultraviolet?

When jumping straight down, you can be seriously injured if you land stiff-legged. One way to avoid injury is to bend your knees upon landing to reduce the force of the impact. A 72.9-kg man just before contact with the ground has a speed of 8.74 m/s. (a) In a stiff-legged landing he comes to a halt in 1.71 ms. Find the magnitude of the average net force that acts on him during this time. (b) When he bends his knees, he comes to a halt in 0.268 s. Find the magnitude of the average net force now. (c) During the landing, the force of the ground on the man points upward, while the force due to gravity points downward. The average net force acting on the man includes both of these forces. Taking into account the directions of the forces, find the magnitude of the force applied by the ground on the man in part (b)

1. A student pulls horizontally on a 12 kg box, which then moves horizontally with an acceleration of 0.2 m/s². If the student uses a force of 15 N, what is the coefficient of kinetic friction of the floor?

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The output voltage of an AC generator is given by ?v = 121 V sin (32?t). The generator is connected across a 0.007 H inductor. Find the following.

(a) frequency of the generator?=____ Hz

(b) rms voltage across the inductor?=____ V

(c) inductive reactance?=____ ohms

(d) rms current in the inductor?=____ A

(e) maximum current in the inductor?=____ A

(f) average power delivered to the inductor?=____ W

(g) Find an expression for the instantaneous current. (Use the following as necessary: t.)

" i=_________ "

(h) At what time after t = 0 does the instantaneous current first reach 1.00 A? (Use the inverse sine function.)?=_____ s

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1. What force does a 1.49*10⁶ N/C field exert on a 2.37 μC charge on a Van deGraaff’s belt?

2. Calculate the angular velocity ω of an electron orbiting a proton in the hydrogen atom, given the radius of the orbit is 0.65×10^-10 m . You may assume that the proton is stationary and the centripetal force issupplied by Coulomb attraction. Give answer in terms of 10¹⁶ rad/s.

3. How many coulombs of positive charge are there in 5.89 kg of plutonium, given its atomic mass is 244 and that each plutonium atom has 94 protons? Give your answer in millions of Coulombs.

4. By what factor must you change the distance between two point charges to change the force between them by a factor of 23? Hint: your answer should be greater than 1.

5. An amoeba has 0.989×10¹⁶ protons and a net charge of 0.5 pC. How many fewer electrons are there than protons? Give answer in terms of 10⁶ electrons.

A marble rolls off a tabletop 0.70 m high and hits the floor at a point 3.5 m away from the table's edge in the horizontal direction.

(a)

How long (in s) is the marble in the air?

__________________________________________ s

(b)

What is the speed of the marble (in m/s) when it leaves the table's edge?

__________________________________________ m/s

(c)

What is its speed (in m/s) when it hits the floor?

__________________________________________m/s

3. A block on an incline is pushed by a hand. The hand exerts a force on the block parallel to the incline. State whether the specified quantities are positive, negative, or zero. Explain in each case.

a. The block moves up the incline and speeds up.The work done by the hand on the block. The work done by the block on the hand.

b. The block moves down the incline and speeds up (even though the hand is still pushing up along the incline.) The work done by the hand on the block. The work done by the block on the hand.

c. The block moves down the incline and slows down. (Note that the hand is now pushing down the ramp, and the ramp has friction.) The work done by the hand on the block. The work done by the block on the hand.

Consider an L-R circuit as shown in the figure. (Figure 1) The battery provides 12.0V of voltage. The inductor has inductance L, and the resistor has resistance R = 150? . The switch is initially open as shown. At time t=0, the switch is closed. At time tafter t=0 the current I(t) flows through the circuit as indicated in the figure.

Part C

What is the current reading I(?) given by the ammeter shown in the circuit (Figure 4) at one time constant after t=0?

Express your answer in amperes.

A spring is compressed by 15 cm, which requires 150 N of force. What is the spring constant of the spring? How much potential energy is stored in the spring? A 20 kg box is attached to the spring. This arrangement is placed such that the spring is horizontal and the box will slide along a frictionless, horizontal track. What is the maximum speed of the box after the spring is released?

explain electromagnetic induction, Faraday's Law, and inductance. Also give examples.

PLEASE DO NOT WRITE IT BY HAND.

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1) Consider a soap bubble with radius, r. The pressure inside the bubble must be greater than the pressure outside of the bubble. The surface tension of the bubble, y, supports the difference in pressure, delta p. Using dimensional analysis, formulate an expression for the pressure difference.

2) In 1945 the first atomic bomb was tested in New Mexico. The destructive power (Energy) of the bomb was kept classified however, following the release of *time* stamped pictures showing the bomb's explosion *radius* a British physicist, G. I. Taylor, was able to estimate the power released by the explosion. Identify the missing parameter and use dimensional analysis to formulate an expression for the Energy.