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# TSR Physics Society watch

1. I don't require neither an A-level nor a detailed explanation. I am/was just curious and want to discuss with people who are interest in physics. Strange, eh?

Although you have explained my questions well, there is another one which I have due to your comment:

(Original post by agostino981)
(...) Note that there is a reaction force of centripetal force on the moon such that it equals to the gravitational force.
(...)
I understand why centripetal force and gravitational force exist in this connection. But I don't understand why reaction force come into being. Would you be kind enough to explain me this connection too?

And then there is another question in terms of astrophysics:
Could it be that the orbits of the planets are inertial systems? In my consideration, the planets have their own (constant) speed in their own orbit to go round the sun. Then the whole solar system would be nothing more than an inertial system.
2. (Original post by Kallisto)
I don't require neither an A-level nor a detailed explanation. I am/was just curious and want to discuss with people who are interest in physics. Strange, eh?
Physics is not for physicists only :P

(Original post by Kallisto)
I understand why centripetal force and gravitational force exist in this connection. But I don't understand why reaction force come into being. Would you be kind enough to explain me this connection too?
Take a look at the wiki article about Reactive centrifugal force

Make an analogy where the string can be thought as the gravitational force.

(Original post by Kallisto)
And then there is another question in terms of astrophysics:
Could it be that the orbits of the planets are inertial systems? In my consideration, the planets have their own (constant) speed in their own orbit to go round the sun. Then the whole solar system would be nothing more than an inertial system.
I am going to assume that you are trying to say that the planets are in inertial frame or not.

Without considering perturbative effects from other celestial bodies, a planet orbiting the sun is following a geodesic with respect to the (metric of) space-time. According to theory of relativity, a body in geodesic is in inertial frame.
3. (Original post by boromir9111)
4. (Original post by dknt)
BRUUDDAAAAAAAAA.....you have me confused with your geek-a-zoid self

5. i ****ing love physics, sorry about the language.

did anyone do the recent aqa physics unit 1 exam
6. I'm sure a lot of people here would be interested in looking at the STEP in Physics from 1998 and 1999
7. (Original post by LogicGoat)
I'm sure a lot of people here would be interested in looking at the STEP in Physics from 1998 and 1999
What's this?

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8. Is anyone free to join this so long as they're connected to Physics?

Currently doing my A2's and have applied for Physics at all 5 of my uni choices :P I live and breathe the subject! This and Maths are the two things which make my academic world go round.
9. (Original post by arcturus7)
Is anyone free to join this so long as they're connected to Physics?

Currently doing my A2's and have applied for Physics at all 5 of my uni choices :P I live and breathe the subject! This and Maths are the two things which make my academic world go round.
It's open to everyone, the only requirement is an interest in physics.
10. (Original post by lion23)
What's this?
The Sixth Term Examination Papers (STEP for short) were exams that were sometimes required for entry into the University of Cambridge. They're based on the A-level syllabus but are aimed at the top 2% (not actually sure of the percentage) of A-level candidates so are significantly harder. Thought they might be interesting for anyone doing A-level physics and looking to challenge themself
11. (Original post by LogicGoat)
The Sixth Term Examination Papers (STEP for short) were exams that were sometimes required for entry into the University of Cambridge. They're based on the A-level syllabus but are aimed at the top 2% (not actually sure of the percentage) of A-level candidates so are significantly harder. Thought they might be interesting for anyone doing A-level physics and looking to challenge themself
Great thanks, will definitely take a look!

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12. I have a question in terms of magnetism. Two north poles of two magnets are opposite and then it comes to a repulsion, as same poles have no attractivity to each other. In my consideration the field lines of the respective magnets go to the respective south pole. Am I right with that?
13. i want to join!!
14. Long time no here. I would just love to know whether a satellite needs escape velocity and escape energy as well as a rocket to come into space.
15. can anyone help me with this problem related to laws of motion? two cars are running in the same direction with the same speed of 30km/hr these two cars are a 5km apart.what is the speed of a third car if it meets the first two cars at an interval of 4 minutes?
16. (Original post by aachal)
can anyone help me with this problem related to laws of motion? two cars are running in the same direction with the same speed of 30km/hr these two cars are a 5km apart.what is the speed of a third car if it meets the first two cars at an interval of 4 minutes?
If the 3rd car is travelling with constant velocity, it will be covering a distance of 5km in 4 minutes, which means it will be travelling with a velocity of 75km/h

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17. (Original post by lion23)
If the 3rd car is travelling with constant velocity, it will be covering a distance of 5km in 4 minutes, which means it will be travelling with a velocity of 75km/h

Posted from TSR Mobile
and i guess that's the relative velocity.the velocity of the car then must be either (75+30)km/hr or (75-30) km/hr dependin on which direction the third car is moving, is it?
18. It's better to start a new thread in the main forum if you have a specific homework or exam question you need help on.
(I see you have done this!)
19. (Original post by Kallisto)
Long time no here. I would just love to know whether a satellite needs escape velocity and escape energy as well as a rocket to come into space.
Do you mean an artificial satellite?
They are launched on a rocket. The rocket needs enough energy to get itself and the satellite into space.
The escape velocity does not depend on the mass of the rocket or satellite, as can be seen from the standard formula.
However, as a rocket is driven over a period of time, the escape velocity formula does not really apply. That formula applies to projectiles.
20. (Original post by Stonebridge)
x
Quite late, but thanks. I meant satellites like Sputnik I. I have found out that satellites move in the east direction, as the earth perform the rotation in this direction. Satellites get quasi an impulse, if they take the direction of earth along. It is a common method to save fuel for acceleration.

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