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  1. K

    You dig a hole half way to the center of the earth. You lower an object to the bottom

    Can someone explain the gamma symbol in the gravitation equation ehild posted ?
  2. K

    You dig a hole half way to the center of the earth. You lower an object to the bottom

    What about ignoring all the layers of the earth above the hole and just using the mass left to calculate the gravitational pull of the earth?
  3. K

    Sound and hearing - conceptual question?

    Stars other than our sun normally appear featureless when viewed through telescopes. Yet astronomers can readily use the light from these stars to determine that they are rotating and even measure the speed of their surface. How do you think they can do this?
  4. K

    You dig a hole half way to the center of the earth. You lower an object to the bottom

    I used the "Inside a solid sphere of constant density the gravitational force varies linearly with distance from the center, becoming zero at the center of mass." from the reference to make my previous suggestion and yes I did get intimidated when I scrolled down from there. Can someone...
  5. K

    What happens to the lost energy in these situations?

    Yea that does help...thanks...but what about question c? Was I right about that? When an object falls some of the PE gets translated into KE which slows the object down right?
  6. K

    What happens to the lost energy in these situations?

    What happens to the "lost" energy in these situations? (a) A box sliding across the floor stops due to friction. How did friction take away that KE and what happened to that energy? (b) A car stops when you apply the brakes. What happened to its kinetic energy? (c) air resistance uses up...
  7. K

    A 1 Kg object is dropped from rest from a helicopter at an altitude of 2000 meters?

    After you solve for v you get 200 m/s. Do you set the KE = to the spring equation after that to find distance it goes into pillows? 1/2mv^2 = kX?
  8. K

    A 1 Kg object is dropped from rest from a helicopter at an altitude of 2000 meters?

    Would it be mgh + 1/2mv2 (1kg)(9.8m/s2)(2000m) + (1/2)(1kg)(v)2
  9. K

    A 1 Kg object is dropped from rest from a helicopter at an altitude of 2000 meters?

    A 1 Kg object is dropped from rest from a helicopter at an altitude of 2000 meters. What is the velocity of the object just before it lands upon a thick bed of pillows? The top of the pillow stack is at zero altitude. If the restoring force constant (spring constant) of the stack of pillows is...
  10. K

    You dig a hole half way to the center of the earth. You lower an object to the bottom

    You dig a hole half way to the center of the earth. You lower an object to the bottom of the hole. By what fraction has the force of the Earth’s gravity on the object been reduced relative to that at the surface? Assume that the earth is a sphere and has uniform density
  11. K

    Moment of Inertia

    Does anyone know why I'm getting a negative t? t = (w-w0)/(angular acc.) (0 - 100)/(.0125 rad/s^2) = -8000 s
  12. K

    Moment of Inertia

    I'm getting a negative answer for time? Why is this I used the w - w0 = at formula
  13. K

    Bernoulli equation (self made diagram)

    .5*density *(0)2 + 0 + 10atm(convert) = constant (.5)(density)(vf)2 + density(g)(y height) + 2atm Would I set these equal and solve for vf?? What about the height of the lake and the height of the pipe?? Do those add more pressure??
  14. K

    Bernoulli equation (self made diagram)

    An object is accidentally dropped into a water pipe. Pressure applied to pipe is 10 atm. The depth of lake is 10m. What will be speed of object when it exits the pipe and first enters the lake? Assume that the object is carried along with the surrounding water and does not affect flow of...
  15. K

    Moment of Inertia

    Fk = ukN so the Force would be (0.5)(1N)? = .5 N?
  16. K

    Moment of Inertia

    I know tau = r x F would you plug 1N for F? and 1 m(radius of sphere) for r? tau = 1N x 1m = 1 N m I = (2/5)(100kg)(1m)^2 = 40 kg m so angular acceleration = tau/I = (1/40) rad/s^2 is this right? How would u use coeff of friction?
  17. K

    Moment of Inertia

    Anyone know?
  18. K

    Moment of Inertia

    Initial angular velocity = 100 rev/s Final angular velocity = 0 I don't know how to get the angular acc. Would you use the torque formula? tau = Iα ? I don't know what tau would be
  19. K

    Pendulum swing from 1deg to 2 deg

    Thanks for the confirmation :smile:
  20. K

    Pendulum swing conserves what?

    How does it show that neither are conserved? Is it because the result is not the same at the top of the swing and the bottom of the swing in both cases?
  21. K

    Moment of Inertia

    How do I get the third variable?
  22. K

    Planets orbit around the sun

    Wouldn't angular momentum be conserved since the Sun doesn't apply any torque to the planet? dL/dt = tau = r cross F r is vector from sun to planet F is directed from planet to sun so cross product would be 0 resulting in constant angular motion
  23. K

    Pendulum swing from 1deg to 2 deg

    A pendulum swings through a maximum arc of one degree in 1 sec. Later, the pendulum is made to swing through a max of 2 degrees. What is the time required for the 2 degree arc? T = 2pi(L/g)^(1/2) Is the time the same since the swing depends on only the length and gravity due to acceleration?
  24. K

    Pendulum swing conserves what?

    x is the cross product in this case. Is r cross product 0 = 0? Sorry I kind of forgot cross product ...so I'm not sure rockfreak, sorry maybe I shouldve restated it in the actual post but the topic title is "pendulum swing conserves what?"
  25. K

    Doubling Celsius temp also double the pressure?

    So we usually talk about Kelvin at around 273K and above which prevents using 0K. Isn't the Kelvin scale directly related to pressure since 0K = 0Pressure? but at zero pressure the celsius scale has a negative value.
  26. K

    Pendulum swing conserves what?

    No Angular momentum : L = r x p At top of swing when v = 0 p = 0 & L = r At bottom of swing p = mv L = r x p So they are not conserved??
  27. K

    Doubling Celsius temp also double the pressure?

    Ok thanks mgb...it makes more sense now....but couldnt you also have 0 Kelvin?? So wouldn't an increase from 0K to 1K do the same thing ?
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