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  1. C

    Conceptual question regarding buoyant force

    I think I got it: For all three fluids, weight of fluid displaced is the same, but Weight = mg = (rho)(V)g Therefore rho is inversely proportional to V. For the fluid of highest density, volume displaced is the least, because just a small volume of this fluid already weights the same as a...
  2. 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...
  3. 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...
  4. C

    Conservative force and potential energy

    U = - integrate [0 to 2] F(y) = - integrate [0 to 2] (3y-6) = (3/2)y^2 - 6y. Substituting the limits I get 6J. Is that correct?
  5. 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...
  6. C

    Effects of frequency on rate of emission of photoelectrons

    Shouldn't the photon rate be constant? I thought it is just the <energy> of the photons that is increasing.
  7. C

    Effects of frequency on rate of emission of photoelectrons

    But why does the book say rate of emission decreases when frequency increases?
  8. 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...
  9. 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...
  10. 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...
  11. 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...
  12. C

    Statements regarding Brownian motion experiment

    Do you mean that when there are less smoke particles, the probability of one particle being bombarded by gas molecules increase so its change of speed increases?
  13. C

    Distance from sources of different intensity to get same loudness

    I think this is the formula needed: Intensity = Power/4∏r^{2} So the intensity of the sound where the person stood was P/256∏. It is now halved. So the power gets halved too. P= 128∏I since P = 4∏r^{2}I 128∏I=4∏r^{2}I r=4√2 Please correct me if I'm wrong.
  14. C

    Statements regarding Brownian motion experiment

    The experimenter wanted to observe the motion of the smoke particles? Apart from smoke there's air molecules in the jar. Regarding my concern about choice A), I think the gas molecules means air molecules?
  15. 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...
  16. C

    Voltage over bulb with broken filament

    During the moment the switch is turned on, is there no current flowing through the first bulb? Charge did flow through the first bulb, only that they're blocked at the second bulb, no?
  17. 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...
  18. C

    Voltage over bulb with broken filament

    Sorry, the second bulb has the broken filament. The voltmeter across the broken bulb would read 240V and that across the good bulb would read 0V.
  19. 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...
  20. C

    Speed of two bodies that sticks together after collision

    From " m(2v) + 3m(-v) = (m+3m)V " 2mv -3mv = 4mV -mv = 4mV V= -v/4 Speed does not have a direction, so answer is v/4. Why wrong?
  21. C

    Stick lying against wall

    Why the reaction force from a hinge can be slanted?
  22. 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...
  23. C

    Forces acting on a hanging peg

    But the inside of the wall can act on the peg in any direction. So if the wire acts on the peg in other directions, the inside of the wall will just automatically balance it by acting in the opposite direction?
  24. 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...
  25. C

    Forces acting on a hanging peg

    The inside of the wall?
  26. 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...
  27. 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...
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