Physics Olympiad (2013) (1 Viewer)

[hungry_soul]

The test was really hard Ill be lucky to get a credit.

 

[hungry_soul]

I failed, last question was a killer :L
the experiment thew me off so I kind of said "can't be bothered" and just stared at the paper for the remainder of the exam...

the last question wasn't that hard imo, it was so random though

 

[hungry_soul]

can someone please explain the mechanics question, i'm in Year 10 and haven't started physics so i had no idea what i was doing. just point me in the direction of the relevant required physics

 

[Thushan]

considering your in Year 10 and haven't started physics that would be a very good achievement! Don't be discouraged, it sounds like the test was hard for everyone!

 

[Thushan]

I can explain the mechanics question if you tell me what it was about. I'm majoring in physics so I should be able to link you in the right direction.

 

[Thushan]

How did everyone else find it?

 

[iStudent]

Guys what did you get for the MCQ question with the 8kg mass hanging down from the pulley and the 5kg mass on the smooth horizontal surface?

For those who didn't do the olympiad today, i'll try to regurgitate the question (with words):

A mass of 8kg hangs from a pulley. It is connected to a 5kg mass that lies on a smooth horizontal table with a string.
Find the acceleration of the 8kg mass (which is hanging beneath the table)
a. 15ms2
b. 9.8ms2
c. 6ms2
d. 3.8ms2
e. forgot (something like 0.5ms2)

 

[Thushan]

Guys what did you get for the MCQ question with the 8kg mass hanging down from the pulley and the 5kg mass on the smooth horizontal surface?

For those who didn't do the olympiad today, i'll try to regurgitate the question (with words):

A mass of 8kg hangs from a pulley. It is connected to a 5kg mass that lies on a smooth horizontal table with a string.
Find the acceleration of the 8kg mass (which is hanging beneath the table)
a. 15ms2
b. 9.8ms2
c. 6ms2
d. 3.8ms2
e. forgot (something like 0.5ms2)

The answer for that is c) 6ms2. That is what I got with my calculations. I can try and explain it to you if you want.

 

[Thushan]

If anyone has any questions feel free to ask me. I can explain anything you like

 

[iStudent]

I put down 3.8ms2 (i know it's wrong) but I think the answer is 9.8ms2 since the table is smooth and there is no force pulling the 8kg mass back up.

What's your explanation to 6ms2?

 

[Thushan]

Both masses are accelerated, one up and one across, but both have an acceleration of a. Since it is a pulley system, they both have the same acceleration. Let their acceleration be a. Two equations can be set up for this, one for the 5kg block and one for the 8kg block.

So let m1 (the mass of the first block) =5kg
and let m2 = 8kg

The net force is equal to the mass x the acceleration or F=ma

1. T=m1 x a (this is the equation for the forces on the first mass)
2. m2 x g - T = m2 x a (this is the equation for the net forces on the second mass)

Using these two equations, T and a can be found.

m2 x g - m1 x a = m2 x a
a = (m2 x g) / (m1 + m2)

substituting these values
m1 = 5kg
m2 = 8kg
a = 9.8

the answer is close to 6ms2.

 

[Thushan]

how did everyone else go?

 

[iStudent]

the last question wasn't that hard imo, it was so random though

how did you design your experiment?
I didn't even bother to include a verb at the start of each method since I got distracted. That test was so weird, it tells you not to hurt your rulers, your pens and it tells you not to eat your test paper - so I was like wtf? and did I forget to mention that pesky rhyme at the end of the test paper?

 

[Andrew Pan]

ahahaha they always have a good sense of humour, at the end of last year's paper it was 'that is all your honour'

 

[Thushan]

ahahaha they always have a good sense of humour, at the end of last year's paper it was 'that is all your honour'

They seem to be pretty funny

 

[Thushan]

What other questions were there??

 

[iStudent]

only received credit for the physics olympiad -.-'
but i guess i should be happy - got distinction for the bio and bronze medal for chem

 

[Kurosaki]

only received credit for the physics olympiad -.-'
but i guess i should be happy - got distinction for the bio and bronze medal for chem

Nice, I got a bronze for chem as well ^___^. Was pretty surprising to hear since I thought I messed up real bad. My school got another bronze in physics and one gold for Chem and another gold for physics. Pretty good since we didn't get trained and just self taught ourselves..

 

[RealiseNothing]

Nice, I got a bronze for chem as well ^___^. Was pretty surprising to hear since I thought I messed up real bad. My school got another bronze in physics and one gold for Chem and another gold for physics. Pretty good since we didn't get trained and just self taught ourselves..

Beast!

 

[Kurosaki]

Haha not really, there was this really easy section (which I still screwed a bit in ). It had a lot of VERY simple calculations, based on how much volume of water gets displaced when you throw some metal into it. And they gave you the density of the metal and everything so it was fairly easy to do.