A steel bicycle wheel (without the rubber tire) is rotating freely with an angular speed of 14.5 rad/s. The temperature of the wheel changes from 142 to 244 °C. No net external torque acts on the wheel, and the mass of the spokes is negligible. What is the angular speed of the wheel at the higher temperature?
In: Physics
Typing The Answer Is Mandatory
Examine the structures of the bulbs to form a conclusion as to the reason that fluorescent bulbs last longer than incandescent bulbs.
In: Physics
Challenge #1: How is electrostatic force (Felect) related to the magnitude of charge on the two objects?
Keeping the separation distance for all trials the SAME, change the magnitude of the charges and record the force.
Charge on 1 (q1) 
Charge on 2 (q2) 
Force (Felect) 
5 C 
200 C 
1 N 
Is the relationship between MAGNITUDE of the electric charge and FORCE different today than it was yesterday? What type of relationship is this? Positive/Negative Linear/Nonlinear 
The arrows in the simulation illustrate the SIZE and DIRECTION of the FORCE. What happens to the DIRECTION of the force when you switch from opposite charges to similar charges? 
Challenge #2: How is the electrostatic force (Felect) related to the separation distance (d) the two charges?
Keeping the magnitude of charge on both objects the SAME, collect data relating distance to force.
Separation Distance (d) 
Force (Felect) 
1 box 

Is the relationship between DISTANCE between the electric charges and FORCE different today than it was yesterday? What type of relationship is this? Positive/Negative Linear/Nonlinear 
In: Physics
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 ydirection. 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.
In: Physics
In: Physics
6. In each situation described below, compare the magnitudes of the two forces. Explain your answer in each case.
a. A 90kg an and a 60kg 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.
In: Physics
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?
In: Physics
When jumping straight down, you can be seriously injured if you land stifflegged. One way to avoid injury is to bend your knees upon landing to reduce the force of the impact. A 72.9kg man just before contact with the ground has a speed of 8.74 m/s. (a) In a stifflegged 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)
In: Physics
1. A student pulls horizontally on a 12 kg box, which then moves horizontally with an acceleration of 0.2 m/s^{2}. If the student uses a force of 15 N, what is the coefficient of kinetic friction of the floor?
2. A 30 kg block slides down a 20° ramp with an acceleration of 1.2 m/s^{2}. What is the coefficient of kinetic friction between the block and the ramp? 3. For a given velocity of projection in a projectile motion, the maximum horizontal distance is possible only at ө = 45°. Substantiate your answer with mathematical support. 4. A stone is projected horizontally at a speed of 6 m/s form the top of a 19.6 m building. What is the final velocity with which the stone would hit the ground? 5. A man swims across the river with a velocity of 2 m/s relative to the flow of water. If the river flows steadily at 4 m/s toward south, what is the velocity of the man with respect to the shore? Solve for both the magnitude and the direction (in degrees). 
In: Physics
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
provide correct answers for five star rating
In: Physics
1. What force does a 1.49*10^{6} 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 10^{16} 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 0.989×10^{16} protons and a net charge of 0.5 pC. How many fewer electrons are there than protons? Give answer in terms of 10^{6} electrons.
In: Physics
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
In: Physics
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.
In: Physics
Consider an LR 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.
In: Physics