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  1. C

    Conceptual question regarding buoyant force

    A penguin floats first in a fluid of density p0, then in a fluid of density 0.95p0, and then in a fluid of density 1.1p0. a) Rank the densities according to the magnitude of the buoyant force on the penguin, greatest first. b) Rank the densities according to the amount of fluid displaced by the...
  2. C

    Conceptual problem regarding pressure and surface area

    Is the air pressure acting on the top of the head of a person standing in a room equal to the air pressure acting on a same area on the floor of the same room? Since F = pA , it seems as if the air pressure is independent of the height of the surface on which it is acting. But that doesn't seem...
  3. C

    Conservative force and potential energy

    Problem: A conservative force F is acting on a particle that moves vertically. F can be expressed as (3y-6) j head N, y is in m and j head is a unit vector along vertical direction. a) Calculate the potential energy associated with F, with the potential energy set to zero at y=0. b) At what...
  4. C

    Effects of frequency on rate of emission of photoelectrons

    Light of constant intensity is incident on a metal surface, causing electrons to be emitted. State and explain why the rate of emission of electrons changes as the frequency of the incident light is increased. My answer: As frequency increases, energy of photons also increases, so more energy...
  5. C

    SHM of liquid in U tube

    The figure shows a U tube of uniform cross-sectional area A containing liquid of density p. The total length of the liquid column is L. When the liquid is displaced by an amount x from its equilibrium position, it oscillates with simple harmonic motion. The weight of liquid above AB provides...
  6. C

    Hypothesis test (binomial) problem

    Homework Statement Hester suspected that a die was biased in favour of a four occuring. She decided to carry out a hypothesis test. When she threw the die 15 times, she obtained a four on 6 occasions. Carry out the test, at the 5% level, stating your conclusion clearly. Homework...
  7. C

    Arrangement of eigenvalues in a Diagonal matrix

    Homework Statement Is it necessary to arrange the eigenvalues in increasing value order? As shown in the image attached, if I arrange my eigenvalues -2, -1, 1 diagonally, my D would be 2^8 , 1, 1 diagonally. However if i arrange it as, say, -1, 1, -2, my D would be different...
  8. C

    Statements regarding Brownian motion experiment

    Homework Statement In an experiment to demonstrate Brownian motion in a gas, a brightly illuminated cell containing smoke is viewed under a microscope. The observer sees a large number of bright specks undergoing random motion. Which one of the following statements about this experiment...
  9. C

    Distance from sources of different intensity to get same loudness

    Homework Statement A point source of sound emits energy equally in all directions at a constant rate and a person 8m from the source listens. After a while, the intensity of the source is halved. If the person wishes the sound to seem as loud as before, how far should he be now from the...
  10. C

    Voltage over bulb with broken filament

    Homework Statement A main circuit contains six similar bulbs connected in series. One of the bulbs has a broken filament. Voltmeters X and Y of infinite resistance are placed in the circuit as shown. What are the voltmeter readings? A) X=0 Y=0 B) X=0 Y=240 C) X=40 Y=40 D) X=240 Y=0...
  11. C

    Stick lying against wall

    Homework Statement A stick is lying at rest against the wall. Which of the following statements is true? A) Friction must be present on both the wall and the floor surfaces. B) The wall surface must be rough, but the floor may be smooth. C) The floor surface must be rough, but the wall may be...
  12. C

    Momentum transfer: Trolley colliding with spring

    Homework Statement A trolley travels with constant velocity to the right on a horizontal ground and collides with a light helical spring attached to a wall fixed to the ground (earth) as shown. At the instant that the trolley comes momentarily to rest during collision, what has happened to...
  13. C

    Speed of two bodies that sticks together after collision

    Homework Statement Two railway trucks of masses m and 3m move towards each other in opposite directions with speeds 2v and v respectively. These trucks collide and stick together after the collision. What is the speed of the trucks after the collision? Homework Equations Conservation...
  14. C

    Forces acting on a hanging peg

    Homework Statement "A picture is supported vertically by a wire that is looped over a horizontal light peg P. There is no friction between the wire and the peg." (Please refer to the image attached) How would the free body diagram of the forces acting on the peg look like? Homework...
  15. C

    How can diffraction occur with gap smaller than the wavelength?

    I was wondering if diffraction of a wave can occur when the gap through which the wave passes is shorter than the wavelength itself. Then I came across this website http://www.talktalk.co.uk/reference/encyclopaedia/hutchinson/m0015966.html Which says that "In order for this effect to be...
  16. C

    Which statement applies to boiling but not to evaporation?

    "Which statement applies to boiling but not to evaporation?" Homework Statement Which statement applies to the boiling but not to the evaporation of a liquid? A The separation of the molecules increases greatly B At normal atmospheric pressure, the process occurs at one temperature only. C...
  17. C

    Heating FeSO4.7H20

    Yesterday I had a practical examination, and one question involves the heating of FeSO4.xH20 to get rid of the water of crystallization to determine the value of x. A crucible was used to contain the crystals. Just a few grams. I had found the value of x to be 7. And now a part of the...
  18. C

    Double slit experiment: effect of changing wavelength

    Homework Statement The question is regarding Young's double slit experiment. "Describe the effect, if any, on the separation and on the maximum brightness of the fringes when the following changes are made. ... ... 2) The wavelength λ is increased to 1.5λ, keeping a and D constant...
  19. C

    Power of car going up an inclined road

    Homework Statement Please refer to the image attached. Homework Equations P=Fv The Attempt at a Solution I have solved the problem already. But when I refer to the marking scheme, I found that they don't accept the use of P=Fv. I understand it's because there's an...
  20. C

    Area under a graph

    Homework Statement Please refer to the image attached. Part (ii) Homework Equations None The Attempt at a Solution My workings are in the second image. I don't understand why is it wrong. Since the graph is well below the x-axis, if I integrate it do I get infinity? (The x-coordinates of...
  21. C

    Range of a function f(x)

    Homework Statement Please refer to the image attached. The first part, (i). Homework Equations None. The Attempt at a Solution My answer is 0 </= x </= 4, but the answer says 0<x<4. Why are 0 and 4 not included? Since the domain includes 6, then 0.5(6)+1 =4, 4 should be included right?
  22. C

    Change in length of wire after adding a load

    Homework Statement Please refer to the image attached. I don't understand why can they just take 1.8m as the original length, since there is already a load hanging there. My calculations yield the value of strain to be e/L, but in the answer it is e/1.8. Please explain this to me. Homework...
  23. C

    Moment about a rigid bar

    Homework Statement Please refer to the image. Homework Equations Sum of clockwise moment=sum of anticlockwise moment The Attempt at a Solution I had drawn out the force diagram and listed out the information required. The question asks me to find force acting by the support B...
  24. C

    Question about Newton's first law

    Homework Statement Q13 All external forces on a body cancel out. Which statement must be correct? A The body does not move. B The momentum of the body remains unchanged. C The speed of the body remains unchanged. D The total energy of the body remains unchanged. Homework Equations The...
  25. C

    Two bulbs connected by a tube with two mercury threads

    Homework Statement Please refer to the image attached. Homework Equations P=hρg The Attempt at a Solution My workings: 16000=h1ρg 8000= h2ρg Since ρ and g are constant, therefore h1:h2 must be 2:1. But the answer is 18:12. Why am I wrong?
  26. C

    Arrangement of circuit affecting resistance measured

    Homework Statement Please refer to the images. First image-question Second image-my interpretation/working. Third image-the answer given. Homework Equations V=IR The Attempt at a Solution In the second image -------------------------------------------- I really don't...
  27. C

    Can area of a triangle be 0.5(c x a) instead of 0.5(a x c)?

    Please see the image attached. Does that have anything to do with directions? The right-hand rule?
  28. C

    Will the formation of a dative bond change the oxidation number?

    Consider NH3, if it forms a dative bond with an H+ to form an ammonium ion, will the oxidation number of N change from +3 to +5? My reasoning is that it uses 5 electrons in bonding. Is that correct?
  29. C

    Can boiling and evaporation occur simultaneously?

    I understand the differences between evaporation and boiling as stated in secondary school textbooks. But I would like to know, can evaporation occur at or above the boiling point? I think that, since evaporation is the escaping of high energy molecules, then when the water is boiling, there...
  30. C

    2 questions about waves (interference, resonance)

    Homework Statement Please refer to the attached image. For the first question, The solution calculated the wavelength,λ by taking the whole length of the string (0.75m) as equal to 3λ/2. What I don't understand is, since the string have to bend to produce a wave, how can we just...
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