What is fluorescence and how is it generated? explain absorption and emission

The two wires carry current i₁ and i₂, respectively, with positive current to the right. The charge q is positive and has velocity v to the right.

True False  If i₁ is greater than i₂, then the force on q is north.
True False  If v = 0, then the force on q is zero.
True False  If i₂ = - i₁ then the force on q equals zero.
True False  If i₂ = 0 and i₁ is greater than zero, then the force on q points into the page.
True False  If i₁ = 0 and i₂ is greater than zero then the force on q is south.
True False  If i₂ = 0 and i₁ is greater than zero, then the magnetic field near charge q points out of the page.
True False  If i₁ = i₂, then the wires are attracted to each other.

8.) When you look at most people

What is the maximum velocity of electrons ejected from a material by 90 nm photons, if they are bound to the material by 4.73 eV?

The figure above shows a portion of the trajectory of a ball traveling through the air. Arrows indicate its momentum at several locations. At these locations, the ball's momentum is: B = ‹ 3.18, 2.88, 0 › kg·m/s C = ‹ 2.7, 1.02, 0 › kg·m/s D = ‹ 2.39, ?0.52, 0 › kg·m/s E = ‹ 2.12, ?1.88, 0 › kg·m/s (a) Which of the diagrams below correctly shows the graphical relationship between B , C , and ? , the change in the ball's momentum as it moves from location B to C? 1 3 2 (b) What is the change in the ball's momentum as it moves from location B to C? ? = kg·m/s What is the change in the ball's momentum as it moves from location C to D? ? = kg·m/s What is the change in the ball's momentum as it moves from location D to E? ? = kg·m/s (c) Between which two locations is the magnitude of the change in momentum greatest? B to C C to D D to E (d) What is this greatest magnitude of the change in the ball's momentum? ? max = kg·m/s

. Charge q1= 1.80*10-8 C is placed at the origin O. Charge q2 = -7.20*10-8 C is placed at point A ( x =0.180 m) as shown in the figures. a.

A charge q3 = 2.5 *10^-8 C is placed at point B ( x = 0.0900 m) as shown in fig.a. Determine the net force F3 exerted on charge q3 by q1 and q2. Give your answer unit vector notation. b. The charge q3 is now placed at point C ( x = 0.270 m) as shown in fig.b. Determine the net force F3 exerted on charge q3 by q1 and q2. Give your answer unit vector notation. c. Find the coordinate xD of a point D on the negative x-axis for which of the net force F3 exerted on q3 by q2 and q1 is zero. Use fig.c. q1 q 3 q2 x fig.a O B A.

1.  Two 3 kg physical science textbooks on a book shelf are separated by 0.25 m. What is the force of gravitational attraction between the books?   

2. What is the force of gravity between two 1000 kg cars separated by a distance of 20 m on a highway?

3. Using the force, calculated in # 2 above, and the weight of the car, calculate:     

Force (from #2) divided by the weight of car   

4. How would the force of gravity between two masses be affected if the separation distance between them is doubled?

5. How would the force of gravity between two masses be affected if the separation distance between them is decreased by one-half?

6. The separation distance between two 2.0 kg masses is decreased by two-thirds. How is the gravitational force between them affected?

7. A man has a mass of 150 kg. What does he weigh on earth expressed in N?

8. If the gravitation constant on the moon, gm is one-sixth that on the earth, how much does the man in # 7 weigh on the moon?

9. An astronaut on the moon places a package on a scale and finds it weight to be 15 N. What would the package weigh on earth?

10. What is the package's mass on the moon?

A 2,200-kg car is moving down a road with a slope (grade) of 14% at a constant speed of 11 m/s. What is the direction and magnitude of the frictional force?
(define positive in the forward direction, i.e., down the slope)?

A 2,282-kg car is moving up a road with a slope (grade) of 10% at a constant speed of 12 m/s. What is the direction and magnitude of the frictional force?
(define positive in the forward direction, i.e., up the slope)?

On a Saturday morning, pickup trucks and sport utility vehicles carrying garbage to the town dump form a nearly steady procession on a country road, all traveling at21.8 m/s. From one direction, two trucks arrive at the dump every two minutes. A bicyclist is also traveling toward the dump, at 4.12 m/s.

(a) With what frequency do the trucks pass him?
?min^-1
(b) A hill does not slow down the trucks, but makes the out-of-shape cyclist's speed drop to 1.56 m/s. How often do noisy, smelly, inefficient, garbage-dipping, roadhogging trucks whiz past him now?
? min^-1

What is the difference between entropy, enthalpy, and heat transfer?

A 145 g mass attached to a horizontal spring oscillates at a frequency of 5.50 Hz. At t = 0s, the mass is at x = 6.60 cm and has v_x =− 35.0 cm/s.

Determine:

a) The maximum speed.

b) The maximum acceleration.

c) The total energy.

d) The position at t = 3.20 s.

Pardon me for my stubborn classical/semiclassical brain. But I bet I am not the only one finding such description confusing.

If EM force is caused by the exchange of photons, does that mean only when there are photons exchanged shall there be a force? To my knowledge, once charged particles are placed, the electromagnetic force is always there, uninterruptedly. According to such logic, there has to be a stream of infinite photons to build EM force, and there has to be no interval between one "exchange event" to another. A free light source from an EM field? The scenario is really hard to imagine.

For nuclei the scenario becomes even odder. The strong interaction between protons is caused by the exchange of massive pions. It sounds like the protons toss a stream of balls to one another to build an attractive force - and the balls should come from nothing.

Please correct me if I am wrong: the excitations of photons and pions all come from nothing. So there should be EM force and strong force everywhere, no matter what type of particles out there. Say, even electrical neutral, dipole-free particles can build EM force in-between. And I find no reason such exchanges of particles cannot happen in vacuum.

Hope there will be some decent firmware to refresh my classical brain with newer field language codes.

A block of mass m1 = 2.9 kg initially moving to the right with a speed of 4.3 m/s on a frictionless, horizontal track collides with a spring attached to a second block of mass m2 = 5 kg initially moving to the left with a speed of 2.8 m/s as shown in figure (a). The spring constant is 572 N/m.

What if m1 is initially moving at 2.2 m/s while m2 is initially at rest?

(a) Find the maximum spring compression in this case. x = m

(b) What will be the individual velocities of the two masses (v₁ and v₂) after the spring extended fully again? (That is, when the two masses separate from each other after the collision is complete.)

Two boxes (m1 = 70.0kg and m2 = 51.0kg ) are connected by a light string that passes over a light, frictionless pulley. One box rests on a frictionless ramp that rises at 30.0? above the horizontal (see the figure below), and the system is released from rest. Find the acceleration of each box.

In a quarter-mile drag race, two cars start simultaneously from rest, and each accelerates at a constant rate until it either reaches its maximum speed or crosses the finish line. Car A has an acceleration of 10.9 m/s2 and a maximum speed of 109 m/s. Car B has an acceleration of 11.8 m/s2 and a maximum speed of 93.7 m/s. (a) Which car wins the race? (b) By how many seconds does this car win the race?