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Physics: Post your doubts here!

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dumbledore.

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A certain organ pipe, closed at one end, can resonate at consecutive frequencies of 640 Hz, 896 Hz, and 1152 Hz. Deduce its fundamental frequency.
 
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dumbledore.

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A pile driver supported by a crane is used to drive a vertical steel girder of mass 900kg into the ground. The pile driver has an 80g steel 'hammer' which is raised 4.0m above the top end of the girder then released to strike the end of the girder and drive it further into the ground. Each impact drives the end of the girder 0.4m further into the ground. Assuming the pile driver does not bounce, calculate:
  1. the speed of the pile driver just before impact? ans: 8.94m/s
  2. the speed just after impact? ans: 0.730m/s
  3. the force of friction on the girder as it penetrates the ground? ans:653N
 
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Metallic9896

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amina1300 said:
:(:(I have the components B B D and an overall C should I give a retake?

In my AS..
Click to expand...

If I were you I would hands down give a retake, given that I'd be aiming for an A*. Even turning this C into a B would be a tougher job. So definitely go for a retake and don't sweat it, you'll do great. I firmly believe any person who has the awareness and dedication to take out time and come to this forum is deserving of an A*. Good luck! :D We're all here to help, feel free to ask any and all queries about any and all matters, whether they are past paper questions or about effective studying techniques. :)
 
Unknown202

Unknown202

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A person uses a surfboard to ride every 30th wave crest towards the beach. The wave crest
travels at a speed of 1.6m/ s and the distance between each wave crest is 24m.
How many wave crests does the person surf in one hour? plzzzzzzzz i need a help in tht question
 
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Metallic9896

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Unknown202 said:
A person uses a surfboard to ride every 30th wave crest towards the beach. The wave crest
travels at a speed of 1.6m/ s and the distance between each wave crest is 24m.
How many wave crests does the person surf in one hour? plzzzzzzzz i need a help in tht question
Click to expand...

Is the answer 8?
 
studyingrobot457

studyingrobot457

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Unknown202 said:
A person uses a surfboard to ride every 30th wave crest towards the beach. The wave crest
travels at a speed of 1.6m/ s and the distance between each wave crest is 24m.
How many wave crests does the person surf in one hour? plzzzzzzzz i need a help in tht question
Click to expand...
Very easy, In fact, it can be solved using IGCSE knowledge

first of all the wavelength(lambda) =24 m
velocity= 1.6 m/s
so frequency = v/(lambda) = 1.6/24 (not going to reduce to decimal, you will know later)

and since frequency = 1/time period so time period = 1/freq =1/1.6/24= 24/1.6 = 15 s

so if every wave takes 15 s and he rides the 30th only this means he will wait 15*30 = 450 s for each 30th wave

his means total of 3600/450 = 8 waves he surf in an hour
hope that helps
 
studyingrobot457

studyingrobot457

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anastasia grey113 said:
http://papers.gceguide.com/A Levels/Physics (9702)/9702_s11_qp_42.pdf
http://papers.gceguide.com/A Levels/Physics (9702)/9702_s11_ms_42.pdf
Q3 part a
i even checked the mark scheme but i still dont seem to get it :/
Click to expand...
I am an IGCSE student, but this seems very easy, if it is to store charge, this means that there should be charge difference in the scalar quantity of both, the very fact that charge moves away when more charge is added means it doesn't store charge, but it does store potential energy of the charge present, meaning that charge is same, in both cases, but it takes energy to get them in a separate way, and it releases energy when they are in the ground state

hope this explanation helps
 
studyingrobot457

studyingrobot457

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Metallic9896

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anastasia grey113 said:
http://papers.gceguide.com/A Levels/Physics (9702)/9702_s11_qp_42.pdf
http://papers.gceguide.com/A Levels/Physics (9702)/9702_s11_ms_42.pdf
Q3 part a
i even checked the mark scheme but i still dont seem to get it :/
Click to expand...

Ahh yeah this is a classic question. Basically something CIE expects you to know and likes to check from time to time.

What does a capacitor do? What actually happens when a capacitor is placed in a circuit? Electrons begin flowing from one end of the circuit, right? Then they hit the first plate and stop. So we have a negative charge on one plate. But what happens next? Electrons from the adjacent plate are drawn away and fed back to the battery, leaving behind a lack of electrons on the second plate, also known as a positive charge. So tell me. Did you store any charge on the capacitor? In all honesty, you didn't. One plate is negative, the other is positive. What does that mena? It means an overall ZERO charge. On the other hand, those electrons reallllyyyy want to cross over through the gap or insulation between the plates and get to the other end, but the capacitor does not allow that, and thus, effectively, maintains a potential difference between the two ends. THIS is how it stores energy. Energy is the capacity to do work. And the capacitor (no pun intended) certainly has that capacity for you can use it to drive a circuit when it discharges. Basically, another way to look at it is that as the electrons accumulate on the negative plate, for the first time, they didn't face any resistance. However, once a good amount of electrons did get there, the next bunch of electrons would feel repulsion, however, the capacitor does work to bring them there and keep the charges separated on the plates. In this way, as it has done work, the energy is stored in it. https://www.quora.com/How-does-a-capacitor-store-energy Try reading this, I hope it helps.
 
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