Indonesian Physics Olympiad

In summary, OP's method leaves the original momentum unchanged, but introduces an external energy that is added to the existing momentum.
  • #1
3
0
Homework Statement
A particle that is moving with velocity ##v## has kinetic energy ##K##. Suddenly the particle gained extra energy externally with magnitude ##3k/16## that causes the particle to split into two pieces. One piece moves at the speed of ##v## relative to the other piece with the direction of motion parallel with the motion before splitting. If the mass of the smaller piece is 1 kg, determine the mass of the other piece.
Relevant Equations
Momentum and Energy
My method is silly but here is my attempt

Initially we know that the kinetic energy is k = ##1/2mv^2## and the final kinetic energy at the moment before splitting is equal to ##(k + 3k/16)mv^2_1 = (19k/16)mv^2_1##. Substituting the value k to the second equation gives us ##v_1 = (\sqrt{19}/4)v##

Since the equation only tells us the relative motion between the pieces, I think we should deal the momentum in the reference frame of that piece. And also notice that ##M = m_1 + m_2## with ##m_1 = 1## This gives us the equation. And there is two cases since we do not know which piece is stationary or moving in this reference frame. So we have to check both case.

Case one, ##m_2## is moving with v relative to other piece.
##(m_1 + m_2)(v_1 - v) = m_2 v
\implies v(1 + m_2)(\sqrt{19}/4 - 1) = m_2 v
\implies m_2 = 0.097 ## which is smaller thus wrong

Case two ##m_1## is moving with v relative to other piece.
##(m_1 + m_2)(v_1 - v) = m_1 v
\implies v(1 + m_2)(\sqrt{19}/4 - 1) = m_1 v
\implies m_2 = 10.23 ## which is bigger thus could right

These all argument could be crap but I wanted to see your solutions.
 
Last edited by a moderator:
Physics news on Phys.org
  • #2
There is no reason to assume that one piece is stationary after explosion. The final kinetic energy may be split between the two pieces.
 
  • #3
SayedD said:
Initially we know that the kinetic energy is k = ##1/2mv^2## and the final kinetic energy at the moment before splitting is equal to ##(k + 3k/16)mv^2_1 ##.
No, the energy after splitting is just ##k + 3k/16##.
 
  • Like
Likes nasu
  • #4
Looking at OP's only previous thread, you can see that @SayedD (OP) never replied to any of the 23 postings made by other PF members.

Let's wait for a reply by OP before making any additional posts to this thread.
 
  • Like
Likes berkeman
  • #5
SammyS said:
Looking at OP's only previous thread, you can see that @SayedD (OP) never replied to any of the 23 postings made by other PF members.

Let's wait for a reply by OP before making any additional posts to this thread.
Thanks for that heads-up, Sammy. OP has been given a not-so-gentle reminder from me to reply to the threads that he starts. Clock is ticking...
 
  • Like
Likes SammyS
  • #6
nasu said:
There is no reason to assume that one piece is stationary after explosion. The final kinetic energy may be split between the two pieces.
In a certain reference frame it is right?
 
  • #7
What reference frame are you using to solve the problem? In what reference frame is the velocity v and the kinetic energy k?
 
  • #8
I have a question of interpretation. It is clear that the energy "gained externally" is added to the existing ##K##. However, I see no definitive indication that this external energy is added in way that leaves the initial momentum unchanged. I would feel more comfortable about it if there were an internal explosion that added the energy instead of an external force.
 
  • Like
Likes SammyS and nasu

1. What is the Indonesian Physics Olympiad?

The Indonesian Physics Olympiad is an annual competition organized by the Indonesian Physical Society (HFI) and the Ministry of Education and Culture of Indonesia. It aims to select students with exceptional physics skills to represent Indonesia in international physics competitions.

2. Who can participate in the Indonesian Physics Olympiad?

The Indonesian Physics Olympiad is open to high school students in Indonesia who are under the age of 20 and have not yet attended university. Participants must also be Indonesian citizens or permanent residents of Indonesia.

3. How can I prepare for the Indonesian Physics Olympiad?

To prepare for the Indonesian Physics Olympiad, you can study the fundamental concepts of physics, practice problem-solving skills, and familiarize yourself with the format of the competition. You can also participate in local physics competitions or join study groups to enhance your skills.

4. What is the format of the Indonesian Physics Olympiad?

The Indonesian Physics Olympiad consists of three rounds: the preliminary round, the regional round, and the national round. The preliminary round is a multiple-choice test, while the regional and national rounds involve theoretical and experimental problems.

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

Participating in the Indonesian Physics Olympiad can improve your problem-solving skills, critical thinking abilities, and knowledge of physics. It can also provide opportunities to network with other physics enthusiasts and potentially open doors for further education and career opportunities in the field of physics.

Suggested for: Indonesian Physics Olympiad

Replies
3
Views
551
Replies
23
Views
2K
Replies
2
Views
1K
Replies
11
Views
207
Replies
5
Views
154
Replies
5
Views
599
Replies
8
Views
474
Back
Top