  # lucy1368

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## Everything posted by lucy1368

1. Hi, For the following question: A 1.37-kg fish is hung from a vertical spring scale with a force constant of 5.20x10² N/m. The spring obeys Hooke’s Law. (a) By how much does the spring stretch if it stretches slowly to a new equilibrium position? ( If the fish is attached to the un-stretched spring scale and allowed to fall, what is the net force on the fish when it has fallen 1.59 cm? © Determine the acceleration of the fish after it has fallen 2.05 cm. http://www.dpcdsb.org/NR/rdonlyres/70ACCCCE-D6A6-44CA-982F-8E319A8ADE82/89746/momentumenergyquestions.pdf (the solution is posted here). I was wondering why you have to use forces to solve(kx) rather than the formula for elastic potential energy(kx/2). When I tried using energy, it did not give me the same answer. Why would energies not work? Thank you in advance for taking the time to answer my question.
2. Hello, So the formula my teacher gave me to solve for constructive and destructive interference of light is d(Xm/L)=(m-1/2)lambda (destructive formula) where m must be a whole number. Is "m" the nodal line number from the central bright? So for this problem, 638nm light is shining through a double slit. The distance from the first node(dark) to the third node is 4cm. Determine the slit seperation if the stance to the screen is 1.2m. So in the example, he solved that sicne D1 to D3 is 4cm, the distance between dark bands is 2cm. However, he used the constructive formula and plaggued in 2cm for the distance from Bo to B1. The constructive formual is d(Xm/L)=m*lambda. Why did he do this instead using the destructive formula which would be using the info from the question?The final answer is 38.3 micrometers btw. I have attached two diagrams; one to explain the eq'n and the other for the problem. Thank you so much!! pHYSICS.bmp pHYSICS.bmp pHYSICS.bmp pHYSICS.bmp pHYSICS.bmp pHYSICS.bmp
3. Hi Mr. Fullerton, Thank you so much for your swift response. However, I am not sure I understand what you mean in: To choose between A or D, look at the function you're using to model the waves and its value at time t=0. With a phase change of 5Pi, you'll have the opposite situation you would have at time t=0. So for a basic cosine function modeled so that the E field has a maximum value at time t=0, at the instant in time where the phase is 5Pi, it would be at a minimum (0) value, so the answer would be A. If you are modeling the wave so that the minimum value is exhibited at time t=0, you would have a maximum magnitude at phase 5Pi. How do you know that the model of a Electromagnetic wave is cosine? Also, how do you know that the mininum vector is at 0(I know this is the only option but is there a way you would know this if the minimum was not given to you)? Thank you so much for taking the time to answer my question!
4. Hi, My textbook asks the question: The phase of an Electromagnetic wave at a point P at some instant is 5pi. Which of the following statements about the field vector is true? A)Both the electric and the magnetic field vectors are 0 B)The electric field is 0 and the magnetic field has its maximum magnitude C)The electric field has its maximum magnitude and the magnetic field is 0 D)Both the electric and magnetic field vectors have their max magnitudes. My question for this question is, is the textbook talking about phase difference? If so, how can the magnetic field and the electric field have a phase difference since it is originating from the same source? Thank you to all who take the time to reply to my question!
5. Hi, I was wondering whether to calculate the potential difference, is V=Electrical energy/charge and V=kq/r for point charges whereas deltaV=electric field*radius. Can u give me a reason to why this is so if this is the case. Thanks!
6. Question: Three charges are placed at the corners of an equilateral triangle with sides of length 2.0 m. The three charges at the corners of the triangle at +4.0 X 10^-6 C, +2.0 X 10^-6 C, and -4.0 10^-6 C. Determine the electric potential at the midpoint of each side of the triangle. What I have done so far: So we know that the formula for electric potential is V=kq/r. So we can just use one of the charges to find the voltage. However, the answer differs depending on which of the 2 charges(which vertices you pick) for each charge. Thank you for taking the time to answer my question.
7. Hi, I was wondering how a Faraday cage works. Why is that that electric fields exist outside conductors and even on the surface of conductors but the field is always perpendicular to the surface of the conductor? Also, in relation to this topic, a conductor with an excess of negative charge is in electrostatic equilibrium. Describe the field inside the conductor. What does it mean for it to be in electrostatic equilibrium. Is it just that the electrons are on the surface of the conductor? if so, wouldn't the inside of the conductor be charged positive because a lot of the negative charge is no the surface. Thank you so much for those who take the time to answer my question!
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