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**Physics...Before/After**

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    #362
    Physics FTW
    Registered Users Posts: 14 ✭Physics FTW


    An0n wrote: »
    That would defeat the purpose of it being in reverse biased silly!

    yes ut surely when it's reverse biased the depletion layer will widen and no current will flow, so how can you get any results


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    #363
    Bears and Vodka
    Registered Users Posts: 2,249 ✭✭✭Bears and Vodka


    Wesc. wrote: »
    You had to place the ammeter beside the diode. I don't think it was phrased too bad tbh.

    It also had to be a microammeter, the voltage from the output had to increase and the resistor was removed.

    Basically this, I think?

    209353.JPG
    Physics FTW wrote: »
    yes ut surely when it's reverse biased the depletion layer will widen and no current will flow, so how can you get any results

    You will get some results if you use a microammeter like on that diagram.


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    #364
    Wesc.
    Registered Users Posts: 715 ✭✭✭Wesc.


    clio94 wrote: »
    Yeah sorry v+u/2 .. The answer seemed pretty big though so wasn't positive ?

    Well the answer I got was in and around the 200 mark or something.. but like to go through 30000 metres in a few minutes he'd want to be going fairly quick alright :P The answer was positive?

    @ Subzero yeah that's what I did just forgot about the microammeter! Thanks anyway :)


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    #365
    BL1993
    Closed Accounts Posts: 341 ✭✭BL1993


    Wesc. wrote: »
    Well the answer I got was in and around the 200 mark or something.. but like to go through 30000 metres in a few minutes he'd want to be going fairly quick alright :P The answer was positive?

    @ Subzero yeah that's what I did just forgot about the microammeter! Thanks anyway :)
    I got like 1432 or something. I found the speed after 13 seconds, and then used v=u+at using u as the speed after 13 seconds and the value you got for acceleration as a and then used v+u/2 :s


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    #366
    Dwellingdweller
    Closed Accounts Posts: 825 ✭✭✭Dwellingdweller


    For the velocity of the skydiver after 13 seconds, I got like 1200 m/s? Then for the five minutes after that, I got like 4000m/s... Definitely not right. Ah well. Maybe the first one's right, but the second one is totally wrong. :P I don't mind though, overall the paper was great, experiments were a peach and I did 3 perfect long questions. Here's hoping for an A2/high B. :)


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    #367
    Wesc.
    Registered Users Posts: 715 ✭✭✭Wesc.


    BL1993 wrote: »
    I got like 1432 or something. I found the speed after 13 seconds, and then used v=u+at using u as the speed after 13 seconds and the value you got for acceleration as a and then used v+u/2 :s

    I think I got that exact figure at the start, but then realised my mistake. Did you take the acceleration to be constant? Because it's not..


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    #368
    Tankosaur
    Registered Users Posts: 102 ✭✭Tankosaur


    what did people say for the magnetic field in a solenoid? I just drew a regular magnetic field.


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    #369
    TheHazer
    Registered Users Posts: 9 ✭TheHazer


    For Q.8 I did it two ways,
    I got the mass of H-2 and H-3 in AMU and converted that to kg and got a change in mass along the equation. I got that and put it into e=mc^2 but i forget what I got for e.

    I also got the protons and neutrons and added their masses.
    I did both ways for Helium too, however all the masses were slightly different!

    What i think is the difference is the electrons, so because they were nuclei, you should have added the protons and neutrons. Not the other way.

    They will probably give marks for both ways however.


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    #370
    Wesc.
    Registered Users Posts: 715 ✭✭✭Wesc.


    Tankosaur wrote: »
    what did people say for the magnetic field in a solenoid? I just drew a regular magnetic field.

    I think it's a coil of wire and you draw the lines going around it.


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    #371
    Tankosaur
    Registered Users Posts: 102 ✭✭Tankosaur


    Wesc. wrote: »
    I think it's a coil of wire and you draw the lines going around it.

    I drew a bar-like structure....

    I think it's just the shape of the mag. field they wanted... so I should get the marks.


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    #372
    BL1993
    Closed Accounts Posts: 341 ✭✭BL1993


    Wesc. wrote: »
    I think I got that exact figure at the start, but then realised my mistake. Did you take the acceleration to be constant? Because it's not..
    I thought it wasn't, but I said in the previous question that that was one of my assumptions. :)


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    #373
    Dwellingdweller
    Closed Accounts Posts: 825 ✭✭✭Dwellingdweller


    Tankosaur wrote: »
    what did people say for the magnetic field in a solenoid? I just drew a regular magnetic field.

    Yep, that's pretty much it. :) Don't think they can take away marks if the solenoid is drawn wrong, as long as you have this down you should be grand.

    sol3.gif


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    #374
    Wesc.
    Registered Users Posts: 715 ✭✭✭Wesc.


    Tankosaur wrote: »
    I drew a bar-like structure....

    I think it's just the shape of the mag. field they wanted... so I should get the marks.

    Yeah so did I.. but my Q5 is so poor so I'm definitely not counting it! Thank f*ck I did the resistance question, it was so easy!


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    #375
    Wesc.
    Registered Users Posts: 715 ✭✭✭Wesc.


    BL1993 wrote: »
    I thought it wasn't, but I said in the previous question that that was one of my assumptions. :)

    So did I, this is where the confusion set in :P This time the question didn't say estimate but "what was", so I didn't want to risk it.


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    #376
    iLaura
    Registered Users Posts: 619 ✭✭✭iLaura


    Dwellingdweller wrote: »
    Yep, that's pretty much it. :) Don't think they can take away marks if the solenoid is drawn wrong, as long as you have this down you should be grand.

    sol3.gif

    You should have seen me in the exam doing the left hand rule to try work out which way it went. I was so confused :P


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    #377
    Wesc.
    Registered Users Posts: 715 ✭✭✭Wesc.


    MatthewRud wrote: »
    Shouldn't average velocity be [1/2(v+u)]/t ? Because its over a duration of t (13 in this case) seconds..

    If you read the question, it says find the average speed during the next 4 minutes and 36 seconds.. So I got the velocity after 13 seconds and then after 4mins36seconds and got the average!


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    #378
    MatthewRud
    Registered Users Posts: 26 ✭MatthewRud


    Wesc. wrote: »
    If you read the question, it says find the average speed during the next 4 minutes and 36 seconds.. So I got the velocity after 13 seconds and then after 4mins36seconds and got the average!

    Sorry, I'm trying to remember the question from memory. Think I did the same, and you are correct. Pain that I had to hand up the paper, can't look over the questions.


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    #379
    BrianC2095
    Registered Users Posts: 34 ✭BrianC2095


    subz3r0 wrote: »
    Deuterium has one proton and one neutron.
    Tritium has one proton and two neutrons.

    Masses of both the proton and the neutron are in the log tables.

    BAZINGA!

    Or you could just use the masses of deuterium and tritium which are in the tables :p


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    #380
    Tankosaur
    Registered Users Posts: 102 ✭✭Tankosaur


    Dwellingdweller wrote: »
    Yep, that's pretty much it. :) Don't think they can take away marks if the solenoid is drawn wrong, as long as you have this down you should be grand.

    sol3.gif


    I drew summit like that but with more lines horizontal to the solenoid it looks right acc. to my book anyway.


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    #381
    Astrozombies
    Registered Users Posts: 145 ✭✭Astrozombies


    "What are the three conditions for an observer to see a rainbow?"

    what even was that.. I said rainfall, dispersion of polychromatic light and .. clear skies? :P


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    #382
    Bears and Vodka
    Registered Users Posts: 2,249 ✭✭✭Bears and Vodka


    BrianC2095 wrote: »
    Or you could just use the masses of deuterium and tritium which are in the tables :p

    In the question it said nuclei i.e. without electrons. Tables have them including electrons.


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    #383
    BL1993
    Closed Accounts Posts: 341 ✭✭BL1993


    Astrozombies wrote: »
    "What are the three conditions for an observer to see a rainbow?"

    what even was that.. I said rainfall, dispersion of polychromatic light and .. clear skies? :P
    Ugh, i said diffraction, interference and refraction. :S


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    #384
    ashh
    Registered Users Posts: 7 ✭ashh


    What was the value for g at 31km above the Earth's surface?
    Is "g = G(mass of earth) / (31,000 + radius of earth)squared = 9.8 E -8" correct? The answer seems very small...:confused:

    And then what was the value for how far he dropped in 13 seconds?


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    #385
    BrianC2095
    Registered Users Posts: 34 ✭BrianC2095


    subz3r0 wrote: »
    In the question it said nuclei i.e. without electrons. Tables have them including electrons.
    Ah yes you're right. Damn I thought that was one of my best questions :rolleyes:


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    #386
    Wesc.
    Registered Users Posts: 715 ✭✭✭Wesc.


    BrianC2095 wrote: »
    Ah yes you're right. Damn I thought that was one of my best questions :rolleyes:

    Yeah so did I.. that was sly enough alright. Feck it anyway! Still, I do think I got an A1.


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    #387
    Tankosaur
    Registered Users Posts: 102 ✭✭Tankosaur


    ashh wrote: »
    What was the value for g at 31km above the Earth's surface?
    Is "g = G(mass of earth) / (31,000 + radius of earth)squared = 9.8 E -8" correct? The answer seems very small...:confused:

    And then what was the value for how far he dropped in 13 seconds?


    g was 9.75 or summit like that


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    #388
    Astrozombies
    Registered Users Posts: 145 ✭✭Astrozombies


    BL1993 wrote: »
    Ugh, i said diffraction, interference and refraction. :S

    hmm seems more logical than my answer :/ It was phrased so badly, I thought they meant weather conditions? haha


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    #389
    Tankosaur
    Registered Users Posts: 102 ✭✭Tankosaur


    Q1 last part

    give two factors which effect the accuracy of the periodic time.

    I said air resistance, there weight of the bob, the size of the bob, the angle it swings in, whether is oscilates in one plane only.

    Anyone have any thoughts/ what did ye say?


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    #390
    Tankosaur
    Registered Users Posts: 102 ✭✭Tankosaur


    Astrozombies wrote: »
    hmm seems more logical than my answer :/ It was phrased so badly, I thought they meant weather conditions? haha

    conditions are sun must be behind you, air must be moist and refraction must occur, acc to my physics teacher anyway.


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    #391
    finality
    Registered Users Posts: 1,763 ✭✭✭finality


    Tankosaur wrote: »
    Q1 last part

    give two factors which effect the accuracy of the periodic time.

    I said air resistance, there weight of the bob, the size of the bob, the angle it swings in, whether is oscilates in one plane only.

    Anyone have any thoughts/ what did ye say?

    the length of the string (a very short length results in a high percentage error) and the angle the pendulum oscillates through


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