(A)at different times a proton and electron are placed equidistant from a point charge.how do the magnitudes and directions of the forces acting on them compare ?why?
(B)how do the accelerations and directions of travel of the electron and proton compare? why?
(C)why are gravitional more important than electrical forces when we calculate the orbits of planets ?why is the electrical force more important than the gravitional force when scientists study interactions at the atomic level?
(D)what explanation is used today to explain how electrical forces are ablr to act upon objects at a distance?
(E)newton's theory explained electrical attraction at a distance .what kind of electrical phenomena at a distance did it fail to explain? how does the modern explanation .account for this second kind of action at a distance?
(F)a compass needle points towards magnetic north because the earth exerts a magnetic force on the compass.does the compass needle exert a force on earth ?if so,is this force larger,smaller or the same as the force that the earth exerts on the compass? explain why in terms of newton's laws?
(G)the frequency of gamma radiation is 10 to the power of 22 Hz. if planks constant ,h, is equal to 6.6*10 (to the power of) -34 J.s, what is the energy of each gamma ray photon? show calculations?(a)the energy of each photon of visible light has about 6.6*10 (to the power of) -19 J of energy .which has a higher frequency ,visible light or gamma rays? give an explanation for your answer based on your knowledge of the relationship between energy and frequency? (b)which has longer wavelength ,gamma radiation or visible light ?(c) if a beam of visible light causes a piece of metal to eject electrons , do you think that a beam of gamma rays would cause the metal to eject electrons? why or why not?
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D) An alternative way to explain the action at a distance is by using a concept of a field. Every electrically charged object creates electric field in space around it. Another object, placed in the field, will then "feel" the force exerted on it by the field, even though it could be far away from the actual source of the field.
This is of course a "classical" explanation. In modern physics, particles and fields are equivalent.
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A. The answer to this question depends upon the identity of the point charge. A point charge is a zero-dimensional electromagnetically charged particle; this means it can be treated as either positive or negative, although its magnitude is usually the same as the elementary charge. In my experience, point charges are usually treated as positive. This means that the point charge will exert an attractive force on the electron, and a repulsive force on the proton (pointing toward and away from the point charge but in the exact same direction relative to each other). The magnitude of the forces is equal because the particles are equidistant from the point charge.
B. Using F=ma, we can see that the proton and electron will accelerate differently; recall that the proton is about 1800 times more massive than the electron. Since the same force is being exerted on both bodies, the force must be distributed among a much larger mass in the proton; thus the acceleration will be parallel to the force vector from the point charge, but the acceleration of the proton will be 1/1800th the acceleration of the electron.
C. Gravitational force is more important on planetary scales because gravitational force is directly linked to mass, and planets have enormous amounts of mass. Additionally, the aggregate electrical charge of a planet is fairly neutral; all of the matter has, presumably, an equal number of protons and electrons, once all matter on the planet is accounted for. On atomic scales, electromagnetic forces are far more important because the gravitational force is many, many orders of magnitude smaller than the electric force.
D. Electrical, and all other forces, are able to act at a distance through the exchange of massless "force carrier" particles known as bosons. The boson for the electromagnetic force is the photon.
E. This question is strangely worded to me, as Newton did talk about light, in terms of a corpuscular (particle) theory, but he didn't really talk about electromagnetism or electricity, subjects that were explored in more detail a century after his death. One thing that the corpuscular theory failed to explain was wavelike behavior of light; the modern theory explains this via photons being variations in a field, which includes values for both particle and wavelike behaviors.
F. In terms of Newton's laws, all actions involve an equal and opposite reaction. The magnet does (and must) exert a force on the earth because it does have a magnetic field of its own; this field is simply too small for us to notice. A good analogy is gravity; you have a gravitational field of your own, which you exert on the earth, but it's too small for us to notice or really care about.
G. You can solve these problems by using these equations;
Gamma ray energy:
- E = hc/lambda
- lambda = c/frequency
Visible vs. gamma ray energy
- lambda = hc/E
- Frequency = c/lambda
- compare your result to the frequency of gamma rays
Wavelength of gamma and visible
- compare the lambda values from the previous problems
- Review Einstein's paper on the photoelectric effect for some hints.
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