Recent content by jcwhitts

  1. J

    What Is the Final Temperature After Dropping Hot Coins into Cooler Water?

    I guess you can assume the final temperatures are equal. I think it was a problem with my signs in that I overcompensated for the fact that the coins lose heat, so they have a negative value for Q. The final temperature will obviously be less than 100 so I suppose that accounts for the sign change.
  2. J

    What Is the Final Temperature After Dropping Hot Coins into Cooler Water?

    You can't assume the final temperatures are the same, sorry. So Qcoins=Qwater but (191*.003)(390)(R-100)=.275(4190)(T-17)
  3. J

    What Is the Final Temperature After Dropping Hot Coins into Cooler Water?

    Homework Statement In a physics lab experiment a student immersed 191 one-cent coins (each having a mass of 3.00 g) in boiling water, at a temperature of 100 degrees C. After they reached thermal equilibrium, she fished them out and dropped them into an amount of water of mass 0.275 kg at a...
  4. J

    Gyroscope- Angular Speed, Rotational Kinematics, Precession

    Figured it out. My approach went off on a tangent because the angular velocity is not constant. Instead, you use the energy approach K=1/2Iw^2 and know that the work is equal to the change in kinetic energy, and Power is work over time. So, Power * change in time =W. 1/2Iw^2=P*t, divide by...
  5. J

    Is My Physics Homework Calculation Correct?

    As long as your first assumption is correct, that power times t is equal to the kinetic energy, you did the integration and the derivations correctly.
  6. J

    Gyroscope- Angular Speed, Rotational Kinematics, Precession

    Gyroscope-- Angular Speed, Rotational Kinematics, Precession Homework Statement A Gyro Stabilizer. The stabilizing gyroscope of a ship is a solid disk with a mass of 6.50×10^4 kg; its radius is 2.30m, and it rotates about a vertical axis with an angular speed of 500 rev/min. 1) How much...
  7. J

    Vector Magnitudes given only direction-help

    Thanks a lot! I was making this question way too hard... I forgot how to solve simple systems of equations. I kept getting 0=0 because when I tried it before, I substituted the variable I solved for into the same equation rather than whichever I hadn't solved initially. Thanks again!
  8. J

    Vector Magnitudes given only direction-help

    Vector Magnitudes given only direction--help! Homework Statement You leave your campsite to go get supplies at a store. You travel 230M at an angle 31 degrees south of east to get there(I'll call this vector A for simplicity's sake). On the way back to camp, you go a distance B at 43 degrees...
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