What Are the Answers to the Physics Olympiad Past Papers?

In summary: Ask a librarian to help you find the books you need.In summary, a student has been entered into a Physics Challenge for GCSE students, despite being a year younger than the intended age group. They are seeking help with understanding a question on the past papers, specifically one involving measuring the half life of a radioactive isotope. The answer is 4 hours, but the student is confused as to how to arrive at that answer. They are also seeking help with the remaining multiple choice questions on the past papers and are looking for resources to further their understanding.
  • #1
Vincit
22
0
So my teacher entered me for the Physics Challenge for GCSE students(test from the makers of the Physics Olympiad, for gifted students), which is intended for students of 16 years of age; year 11. I'm 15, and I'm in year 10, so i don't know why my teacher entered me..

Anyway, I have to self-learn this before january, so I'm here to ask for help after going over the past papers and being completely befuddled..

2. A student performs an experiment to measure the half life of a
radioactive isotope. First they use a suitable detector and counter and
measure the average background radiation to be 120 counts per minute
(cpm). Next they measure the activity with the radioactive isotope in place
and the record a reading of 1080 cpm. Finally they repeat the experiment
12 hours later with the radioactive isotope still in place and record a count
rate of 240 cpm.
The half life of the sample is approximately:
A. 6 hours
B. 4 hours
C. 3 hours
D. 2 hours
E. cannot be determined from the given information

The answers is B.4 hours, and I don't know why. 240 doesn't go into 1080, and that is why I'm so confused.

All of the questions are found here:

http://www.physics.ox.ac.uk/olympiad/Downloads/PastPapers/BPhO_PC_2008_QP.pdf

I need help with ALL OF THEM!(Multiple choice questions) If someone could please explain each answer for me, then I would be so grateful.

The answers are :

1.A
2.B
3.D
4.B
5.C
6.E
7.A
8.A
9.B
10.D

I don't know how to get any of them though, except for question 1. I'm only 15 so don't ridicule me :/
 
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  • #2
For 2, you have to correct for the average background radiation.
 
  • #3
espen180 said:
For 2, you have to correct for the average background radiation.

how would i do that?
 
  • #4
By subtracting it from the measurement. Remember that you want to measure the counts that are due to your sample and want to filter out any other sources.
 
  • #5
espen180 said:
By subtracting it from the measurement. Remember that you want to measure the counts that are due to your sample and want to filter out any other sources.

so 1080-120=960

960/2=480
/2=240

2 x halflife =12 hours

halflife= 12/2

halflife= 6 hours.. so how is it 4?
EDIT: forgot to subtract from 240!

960/2=480
/2=240
/2=120

so 3 x halflife= 12 hours

halflife= 12/3

halflife= 4 hours!

Thank you, now the rest!
 
  • #6
Subtract it from both measurements. You have 960 cpm initially and 120 cpm after 12 hours.

960 /2 = 480
480 /2 = 240
240 /2 = 120

That's 3 "halfings" in 12 hours, so the average halflife is 12 hours / 3 = 4 hours.
 
  • #7
espen180 said:
By subtracting it from the measurement. Remember that you want to measure the counts that are due to your sample and want to filter out any other sources.

novop said:
Subtract it from both measurements. You have 960 cpm initially and 120 cpm after 12 hours.

960 /2 = 480
480 /2 = 240
240 /2 = 120

That's 3 "halfings" in 12 hours, so the average halflife is 12 hours / 3 = 4 hours.

yup, I just worked it out in the previous post. Help me with the rest :)
 
  • #8
Try it yourself first. Post your attempts at a solution and we'll help you on the way. That's how you learn. If you learn how to do a problem by doing it, you can do it on the exam. If we give you the answers, chances are you'll get stuck.
 
  • #9
espen180 said:
Try it yourself first. Post your attempts at a solution and we'll help you on the way. That's how you learn. If you learn how to do a problem by doing it, you can do it on the exam. If we give you the answers, chances are you'll get stuck.

I've tried but cannot find any solutions at all.
 
  • #10
Then you should consult a textbook, not a forum. Check your school library for physics books and read on Wikipedia.
 
  • #11
espen180 said:
Then you should consult a textbook, not a forum. Check your school library for physics books and read on Wikipedia.

It's the summer holidays and I have no textbooks including any of this stuff! Wikipedia is too convoluted for me..

Why shouldn't I consult a forum? If I'm correct, this is a physics forums, here to offer help and answer questions. If that's not what it is for, then sorry.
 
  • #12
You are right, but people here generally don't have the time to explain every one of those problems to you unless you do most of the work yourself.

If I were you, I'd consult my local university and use their library.
 

FAQ: What Are the Answers to the Physics Olympiad Past Papers?

1. What is the Physics Olympiad?

The Physics Olympiad is an international competition that tests high school students on their knowledge and problem-solving skills in physics. It is organized by the International Physics Olympiad (IPhO) and consists of theoretical and experimental exams.

2. How can I prepare for the Physics Olympiad?

To prepare for the Physics Olympiad, you should have a strong foundation in physics and mathematics. Practice solving challenging problems and familiarize yourself with the format of the competition. You can also join a study group or participate in training camps to improve your skills.

3. What are the eligibility requirements for the Physics Olympiad?

The eligibility requirements may vary depending on the country or region you are participating in. Generally, participants must be high school students who have not yet started university. They should also be proficient in the language used for the competition and have a passion for physics.

4. How is the Physics Olympiad scored?

The Physics Olympiad is scored based on the students' performance in both the theoretical and experimental exams. Each problem has a certain number of points assigned to it, and the maximum possible score is 50. The scores are then used to determine the winners and participants who will receive medals and certificates.

5. What are the benefits of participating in the Physics Olympiad?

Participating in the Physics Olympiad can provide many benefits, including improving problem-solving skills, gaining a deeper understanding of physics concepts, and building a network of like-minded individuals. It can also open up opportunities for scholarships, internships, and admission to top universities.

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