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  1. Lukeblackhill

    Heat during the Day

    Hi! My question is: I understand that at noon-day it’s hotter because of the angle with which sun rays enter our atmosphere. But at the same time, I was wondering that the band of radiation responsible for heating things is infrared, and that at noon basically all bands of lower frequency than...
  2. Lukeblackhill

    I Source of Energy in a Field of Forces

    Could you explain that in more detail, please? I haven’t found a good material on the matter.
  3. Lukeblackhill

    I Source of Energy in a Field of Forces

    good evening! My question is the following: it is well stated that energy is conserved in any isolated system, and we can in most circumstances expand our system to a many-steps conversion of energy, but always conserved. The classic example could be the energy of the sun stored in form of...
  4. Lukeblackhill

    I Changes in Hooke's Law

    Morning, I've come across this statement in Berkeley Physics Course, Vol.1 - Cp. 5 (pg.149): "For sufficiently small displacements such a force may be produced by a stretched or compressed spring. For large elastic displacements we must add terms in higher powers of x to Eq. (,5.19): Fx = -...
  5. Lukeblackhill

    B Who drew the first model of the atom?

    The first scientist to have a glimpse of the true nature of the atoms was Rutherford. In his experiments (called the Geiger-Mardsen experiments) in 1908, when using golden foils and alpha particles he was able to determine the localization of the positive part of the atom, as the centre of it...
  6. Lukeblackhill

    Question regarding pressure and energy

    If you apply a force in a body of volume V, in its area surface A, the body experiences a pressure P=F.A that acts in it in order to peform one or more of this actions, such as a. expanding, b.contracting, c. deforming, d.heating, etc. In all cases, the P.V = W, that is the work done on the...
  7. Lukeblackhill

    Symmetries and Conservation Laws

    I've been caught by a quite interesting statement of Berkeley physics Course Vol.1 (Chap. 5), that says "In the physical world there exist a number of conservation laws, some exact and some approximate. A conservation law is usually the consequence of some underlying symmetry in the universe."...
  8. Lukeblackhill

    I Where does the energy go to?

    Thank you, @sophiecentaur.
  9. Lukeblackhill

    I Where does the energy go to?

    Morning, I was thinking about a simple example of inelastic collision: A ball of mass m1, moving with a certain velocity v1, collides and sticks with another mass m2, at rest. The whole system (m1 + m2) will then move with a certain speed v3. If we take m1=m2, so that after the collision we...
  10. Lukeblackhill

    Reduce Kinetic Energy Losses when Two Objects Collide

    I'll try the super-balls, @anorlunda Thank you!
  11. Lukeblackhill

    Measuring Velocity

    The idea of the camera is good, @Orodruin. I'll try that. I will also give a look about this Stroboscope. Thank you.
  12. Lukeblackhill

    Reduce Kinetic Energy Losses when Two Objects Collide

    I'd like to know which methods I could use to reduce the loss of kinetic energy when two iron balls collide, or when a plastic ball collides with the floor after a free fall. I have tried to cover the floor with a fabric that would make it more elastic, but it had a small effect (if it hat...
  13. Lukeblackhill

    Measuring Velocity

    Morning! I was performing some experiments about impulse and conservation of mechanical energy, and for that I was looking to good ways of measuring the velocity of a sphere under the action of a force. In free fall, having the height H it was falling along, I have used the formula v =...
  14. Lukeblackhill

    B "The Galaxy" vs Milky Way

    Thank you @CygnusX-1 , your answer was enriching.
  15. Lukeblackhill

    B "The Galaxy" vs Milky Way

    Good Morning, I've got a doubt originated from a statement of Berkeley Physics Course, Vol.1 - Mechanics, pg. 107, where in a footnote we read, "The systems are called galaxies, that one which contains our own sun is known as the Galaxy. The Milky Way is part of our galaxy". I've always...
  16. Lukeblackhill

    I Separation of Fluids in a Centrifuge

    Morning Mates, I have a question based in a statement take from Berkeley Physics Course, Vol.1 - Mechanics, pg. 102-103, where it reads, "Suspended molecules whose density (mass/volume) is different from that of the surrounding liquid will experience in the ultracentrifuge cell a strong force...
  17. Lukeblackhill

    Range of Mortar Shells

    Thank you @TSny, that was rather helpful.
  18. Lukeblackhill

    Range of Mortar Shells

    Morning Mates, This problem of Berkeley Physics Course, Vol.1 - Chap. 3, says, "Range of mortar shells. The following are experimental data on the range and muzzle velocity of mortar shells, all fired at 4.5 0 to the horizontal. The time of flight is also included. Compare these ranges and...
  19. Lukeblackhill

    Ceiling height for a game of Catch

    Dear Mates, I was studying Newton's Laws of Motion by Berkeley's Physics Course, Vol. 1 - Chap. 3, when I came across this problem, about finding the maximum separation of the boys. In my mind, it was simply about finding the "2x", considering x to be the distance between the first boy and the...
  20. Lukeblackhill

    Developing more practical insights into real situations in Physics

    Good Evening Mates, I've been following up with the Forum for a couple of months now, and I've noticed how some of the members are able to give some deep answers for seemingly simple questions. I'm in my second year of undergrad's school, and have studied the basis of Mechanics, Thermodynamics...
  21. Lukeblackhill

    Galileo's Experiment with an Inclined Plane

    Morning mates, I've peformed Galileo's experiment with inclined planes, using a ramp of 88cm (divided in 4 parts of 22cm), inclined by a height on the right-edge of 4cm. I've measured the following, 1/4 of the ramp (22cm): 1.75s (error of 0.1s) 1/2 of the ramp (44cm): 2.70s (error of 0.1s) 3/4...
  22. Lukeblackhill

    Heat and Sound

    Thank you @jbriggs444 , that was enlightening.
  23. Lukeblackhill

    Heat and Sound

    But in principle, would it be possible to arrange mechanical variables such as mass and speed to define heat, sound, etc?
  24. Lukeblackhill

    Heat and Sound

    Morning! My question is this: If we consider a situation of mechanical collision, in the real world we shall observe certain loss of energy into heat or sound. Can we find mathematical equations to measure the amount of sound or heat produced using only mechanical variables, such as mass...
  25. Lukeblackhill

    Energy required to accelerate itself

    @greypilgrim, as our friend PeroK said, if you consider the car itself, You'll always be talking about a frame at rest. The car applies the same force (and by consequence, the same energy) than any other external object would, for the law doesn't consider sources, but the frame of reference. So...
  26. Lukeblackhill

    I Why there's No Unified Theory ?

    @Arman777 , our current unified fiel theory comprises electromagnetism, the week nuclear force and the strong nuclear force. The problem of gravity is, first...its order of strength is much smaller than the other ones. That means that, on atomic and subatomic scales (where the other forces may...
  27. Lukeblackhill

    Problem with the Definition of work

    I may be wrong, but on the treatment of the 2nd law, (at least for non-relativistic systems) we have a vector as the product of a vector by a scalar F=ma. In the treatment of work, we have the scalar product of two vectors, resulting in a scalar F.d = W. I don't know if such consideration has...
  28. Lukeblackhill

    I What happens if two black holes collide

    @ohwilleke, it's not a mistake of spelling. In fact, I read about it in an article written by a Brazilian physicist, and that seems the way they write. I haven't read it in english, so I did not know how to write it.
  29. Lukeblackhill

    I What happens if two black holes collide

    @Dalton Peters, there's a theory which ascribes the existence of particles called Takions, which in theory has a mirror-sort of symmetry with the Lorent'z invariance. That means that Takions move faster than the speed of light and suffer the same effects einstein's predicted for normal...
  30. Lukeblackhill

    What is the electrostatic force field?

    I agree @ZapperZ, the definition I gave is merely to give a sense about the electric field and what it is.