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  1. J

    Change in Capacitor for largest possible Current

    Homework Statement The capacitor is changed so that the largest possible current is supplied by the source. Enter the value of the capacitive reactance when this change is made. Give your answer in Ohms (Ω). A unit is not required with your answer. Homework Equations The circuit is powered by...
  2. J

    Resistance of Patient

    This question follows: <https://www.physicsforums.com/threads/charge-stored-on-a-capacitor.948193/>
  3. J

    Resistance of Patient

    Homework Statement When the defibrillation shock is applied, the capacitor discharges through the patient as shown in the diagram below: The fraction of charge remaining on the capacitor 1.00 ms after it begins discharging is 0.300. Calculate the resistance of the patient. Note: This will...
  4. J

    Charge Stored on a Capacitor

    Homework Statement Defibrillation[/B] is a common treatment for life-threatening cardiac arrhythmias and ventricular fibrillation. The defibrillator applies a current across the heart (shown by the red arrows in the image below) for a short time (a few milliseconds), disrupting the arrhythmia...
  5. J

    Net Charge on a Magnesium ion

    Homework Statement Calculate the net charge on a magnesium ion which has lost two electrons. 2. The attempt at a solution I put 2+ as my answer and this is what I was told, but I don't understand what they mean by the following; That's a chemist's shorthand, not the amount of charge on the...
  6. J

    Plane Mirror - distance

    The image is 2 x the distance from the mirror so my answer would be 2 x 3.05 = 6.1 m
  7. J

    Plane Mirror - distance

    Would this mean that I need to use the following equation instead??? 1/d0 + 1/di = 1/f ???
  8. J

    Plane Mirror - distance

    All I've been given for this question is what I gave you. di is the distance the image is seen from the mirror. The camera is held by the said person taking the picture. I assume distance from the mirror to focus???
  9. J

    Image Distance

    Homework Statement You look at yourself in a shiny Christmas tree ball, which has a diameter of 9.63 cm. If your face is 7.81 cm away from the shiny ball, calculate the image distance. Homework Equations ??? Thinking I would use magnification = di/d0 di = 0.0781m d0 = 0.0963m The Attempt at...
  10. J

    Plane Mirror - distance

    Homework Statement Suppose that you want to take a mirror selfie, standing 3.05 m in front of a plane mirror. Calculate the distance that the camera will focus to, to get a clearly focused image of your beautiful self. Homework Equations d0 = di The Attempt at a Solution Would I be correct...
  11. J

    The Distance to the seabed

    Yes, it's half the time because we are only want the time to get to the sea bed, whereas we were given the time to reach the seabed and come back to the boat.
  12. J

    The Distance to the seabed

    The answer was using: 1480 x (1/2 x 0.461) = 341 m
  13. J

    Time for radio signal to get to a receiver

    Sorry the answer was 5.83 x 10^-5 s hahah :), thank you.
  14. J

    The Distance to the seabed

    Homework Statement A depth sounder on a ship measures the distance between the bottom of the ship and the seabed using a high-frequency pulse of sound (sonar stands for SOund Navigation And Ranging). Sound travels through water at 1.48 km/s. Calculate the distance to the seabed if the...
  15. J

    Time for radio signal to get to a receiver

    Homework Statement A radio transmitter is located 17.5 km away. The broadcast signals travel at the speed of light (c = 3.00 x 108 m.s-1) through the air towards a radio receiver. Calculate the time it takes the radio signal to travel from the transmitter to the receiver. Homework Equations...
  16. J

    Thermodynamics - Hypothermia - Heat loss

    Im not sure whether the equation I'm using is right or whether I need to use a new equation and what given numbers I should be using???
  17. J

    Thermodynamics - Hypothermia - Heat loss

    Sorry, but I have absolutely no idea where to go from this...
  18. J

    Thermodynamics - Hypothermia - Heat loss

    Is this how I would calculate it then??? t = Q x L/ k x A x delta T = (51.5 x 0.047)/(0.038 x 1.3 x 2) = 24.5 s converted to hours = 0.00681 hours????
  19. J

    Thermodynamics - Hypothermia - Heat loss

    Sorry again, found that there was a question about calculating how long it will take this sheep to develop hypothermia if left outside on this cold day. With the final answer in hours. Same numbers given as shown above at the start of my original forum. I have attempted the question, and told...
  20. J

    Thermodynamics - Hypothermia - Heat loss

    Thank you :), got the question right... it was 39 + 10 = 49 C
  21. J

    Thermodynamics - Hypothermia - Heat loss

    Hi :), thank you for your help. No there is not a second question relating to how long it takes for the sheep to develop hypothermia. Also, with the change in temp (delta T) which of the following calculations would be correct??? delta T = -10 + 39 = 29 C or delta T = 39 + 10 = 49 C ???
  22. J

    Thermodynamics - Hypothermia - Heat loss

    Homework Statement A careless farmer sends this sheep out to graze on a very cold winter day when the temperature is -10oC. The sheep's coat has a thickness of 4.7 cm and a surface area 1.3 m2. Calculate the rate of heat loss from the sheep on this cold day. Assume that heat is lost only...
  23. J

    Simple Harmonic Motion - Speed

    Sorry, worked out how to do it now, it required me using the kinetic energy I had worked out in the previous question. Thank you though :)
  24. J

    Simple Harmonic Motion - rearranging equation

    Thanks, I wanted to find k but worked out how to rearrange it :)
  25. J

    Simple Harmonic Motion - Speed

    To calculate speed for an object in SHM as it moves through equilibrium position, given m of object= 0.505kg, k= 45.08248265, T (period) = 0.665s ???
  26. J

    Simple Harmonic Motion - rearranging equation

    Homework Statement How to rearrange following equation? Homework Equations f = (1/2pi) square root of (k/m) The Attempt at a Solution (f^2 x m)/ (1/2pi)^2 Is this how i would do it?
  27. J

    Simple Harmonic Motion - Speed

    What equation would you suggest I use then???
  28. J

    Simple Harmonic Motion - Speed

    Homework Statement Calculate the speed of the block in SHM as it moves through equilibrium position. k= 45.08248265 N/m m of block = 0.505kg T = 0.665s Homework Equations w= the square root of (k/m) ??? The Attempt at a Solution w = the square root of (45.08248265/0.505) = 9.448398958 =...
  29. J

    Thermodynamics: Dropping a hot horseshoe into a pot of water

    Sorry, that my answer from that I rounded to 3 sf so that wasn't my final answer as it is not 3 sf
  30. J

    Thermodynamics: Dropping a hot horseshoe into a pot of water

    Worked out that the answer for this question is just = 57241.38 J rounded to 3 significant figures. :)
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