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  1. K

    Average Speed/Velocity

    Velocity = distance / time. As long as your time is not zero, it is defined. It's only the denominator that needs to be non-zero. The average speed is the total distance traveled divided by total time spent traveling. The velocity is similar, only it involves the total distance traveled in a...
  2. K

    Why speed of the railroad hopper is the same? [please help]

    Could you explain why exactly the velocity would increase? I believe the equations you posted in your original post are correct.
  3. K

    Why speed of the railroad hopper is the same? [please help]

    I think the problem assumes that there is zero force acting on the car. Rather, there is only an initial velocity: like if you pushed a toy car and let go.
  4. K

    Why speed of the railroad hopper is the same? [please help]

    Yes, the car lost momentum. Perhaps you could explain why do believe the speed would change.
  5. K

    Conservation of Mechanical energy

    In other words, what you need is an expression for the potential energy of a chain segment in terms of the displacement of that chain segment (a segment hanging 5 inches down would have displacement of 5 inches). Now, integrate that over the entire portion of the chain which is displaced.
  6. K

    Conservation of Mechanical energy

    An integral is essentially like doing a lot of addition. Think for example that each chain link is 0.05 m long, and weighs 0.1 kg. Assume five links are hanging off the edge. Think about each chain link is being pulled up discretely. The first link must be moved 0.05m, the second must be...
  7. K

    Physics lab colliding two cars into each other

    Graphs of what? Graphs can often compare two, three, or even more different values or measurements.
  8. K

    Force vs. time

    Typically impulses are used with inelastic collisions, such as a projectile hitting another object and indenting it somewhat. For example, imagine dropping a golf ball into a bowl of sand. Please be more specific as to which forces you are trying to calculate. If it is a homework problem...
  9. K

    Circuit analogue to Kinetic motion.

    It's actually quite simple and very hard to hint at, so I'll just say it. If you have a capacitor-inductor (L-C) circuit, the overall voltage and current will oscillate according to time as the energy is transferred between the inductor's magnetic field and the capacitor's electric field. Once...
  10. K

    Potential Energy of Charge

    Wrong. Charges always want to move with the field. Potential is dependent only upon the change in x-value, NOT y.
  11. K

    Where the ball will fall?

    This is intro physics. Air has no resistance. Ever.
  12. K

    Physics student in need of some help

    0.8 m/s is the man's initial velocity, it seems to be a straightforward application of the equation relating distance and acceleration: \[ d = v_0 + {\textstyle{1 \over 2}}at^2 \] -t will be the time it takes the cockroach to reach its shelter -distance will be the distance the person needs...
  13. K

    Newton's law of cooling

    I really doubt that the lab would be at 212 degrees fahrenheit. The question is asking whether it takes longer to go from 150>>100 or from 100>>50 in an environment that is 20 degrees to start with. Temperature loss occurs the faster at bigger differences, and slower when close to equilibrium.
  14. K

    Solving Mechanical Waves

    Is this the exact wording of the problem? If the two points are simply "within" one wavelength of each other, then it could really be anything. The information that you stated is not enough to calculate the wavelength. Are you sure there is no more information, such as the wave speed, the...
  15. K

    Charge on capacitors in a circuit?

    The voltage from point a to point b is +28V. Each capacitor has a capacitance of 4.00uF (microfarads) What is the best way to calculate the charge on each capacitor?
  16. K

    Gas Question

    The ideal gas law is PV = nRT. As you can see from it, the pressure will increase with decreasing volume, however the temperature doesn't need to change at all.
  17. K

    Conservative and non-conservative forces

    http://en.wikipedia.org/wiki/Conservative_force
  18. K

    Tension force

    F=ma force equals mass*acceleration
  19. K

    Calculating Speed with Kinematics

    Try using this equation: D = VoT + 1/2AT^2 Where Vo is the initial velocity. Once you find this, it is fairly straightforward to calculate the final velocity. Or, for a simpler method, just enter it as a positive acceleration and Vo will work out to be the final velocity!
  20. K

    Increasing speed by 5 mph saves 10 mins?

    Can you work through it for me? I keep getting time1=10+2*speed1...
  21. K

    Increasing speed by 5 mph saves 10 mins?

    If a person drives the same distance twice, and saves 10 mins by driving 5mph more the second time, what is the distance and the speeds?
  22. K

    Equation for Sound wave power.

    Wouldn't it just be the amplitude of the wave?
  23. K

    What was the weight of the person?

    You need to figure out the coefficient of friction. Once you have this, just use your work formulas to figure it out.
  24. K

    HELP I'm struggling in physics

    Not everybody is "Science Smart", but don't sell yourself short. Everybody is good at something, this just happens to be a science forum. I think you'd be more right to say "science is not my thing". Anyway, tell us what YOU know so far. Formulas and such that you know of.
  25. K

    Jogger Vs. The Oak Tree

    This is a simple application of an impulse. I = Force * time, and is also the change in momentum. Momentum is mass times velocity. Momentum before = 81.9 * 4.7 = 384.93. Momentum after=81.9*-4.2= -343.98. Impulse = 728.91 = force * time. Time=.46. 728.91=force * .46. Force is then equal...
  26. K

    Escape Velocity constant?

    I have always wonder how escape velocity is defined - I thought gravity had infinite 'reach'?
  27. K

    Two watches, one thrown in the air.

    He was asking a theoretical question and wanted a theoretical answer. Many people need to stop being rude by saying "there wont be any difference". A theoretical question is used to grasp the concept, even if it is unable to be performed. clearly he is trying to learn something here.
  28. K

    Motion in two dimensions question

    I think they mean that G is just a point, and it's distance from F can be varied, although it start 1/8 of the track from F. But again, that's just how I interpreted it, we can all agree they stated whatever they meant to say very poorly.
  29. K

    Math Problem No Numbers ?

    Precisely the reason why. Because some people feel they need to re-post the right answer for seemingly no reason ;). Joejo, answer these problems. Simplify these so there is no fractions, only exponents: x^2 *x^{-5} = ?? \frac{x^7}{y^4} = ?? Answer those and we will be able to...
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