2016 PSLE Discussions (Born in 2004)

[SuperDadandMum]

Oct 17-20

[ChiefKiasu]

Ender:

If there's no gravity , out in space. Your fart will definitely push you in the opposite direction without stopping. You be lost in space. Like what they show in the movie Gravity and The Martian. Little burst of air will propel the astronaut in one direction.

:rotflmao: While I'll accept your theory, in reality, if you fart in space, you will only be doing it within your space suit, which will act to counter the force. So other than the inconvenience of cohabiting with your own stink, I seriously doubt it will make you fly off to the end of space...

PS. Matt Damon is my hero!

[James Ang]

The PSLE is over for most of our dear P6 children, go celebrate and have fun

Concerndad:

snuggles2009:

Balloon question: my child said kinetic energy makes the balloon move then gravitational pulls it down
Weight/spring question: my child said change to longer spring

Q1 Imho..
The balloon possessed Kinetic Energy to convert into Gravitional Potential Energy. Hence balloon continued to rise even after the balloon was deflated.

Q2. I think it should not be longer spring.

Change the spring into one that has lesser flexibility. So that it can receive a larger elastic spring force of up to 50kg weight limit.

[Mascifun]

First part of the balloon question asked why the rocket toy continued to travel upward despite the balloon being fully deflated.


This was due to the fact that the toy still possessed Kinetic energy at that point of time. Kinetic energy of the air escaping from the balloon was converted to kinetic energy of the toy. The kinetic energy of the toy was then converted to Gravitational Potential energy as the toy moved up. Due to air resistance, some of the kinetic energy is also converted to heat.

Second part of the question asked why the balloon darts around when released. If you make use of the context given in part one, the main difference is that the balloon is no longer encapsulated inside a solid with definite shape. Without the toy rocket holding the balloon in a fixed position, the air escaped from the balloon in different direction, causing it to dart around.

[Ender]

James Ang:

suggested answer for discussion (due to lack of information on the actual question asked in the exam) is

1) When the air is released from the balloon, a forward force is produced in the direction opposite to the direction of air travel. So the balloon moves in a different direction which is opposite to the direction of air travel.

:

No one has the actual question? You interpret 'different direction' as opposite direction. hence Newtown 3rd law applies.
My 1st impression was it was going in different directions (note pural). Hence aerodynamics of asymmetrical drag force and propulsion is not along the line of the ballon's C.G applies, as it has indefinite shape, and it C.G is shifting all the time. In simple term, \"no fix\" shape of the ballon applies.

[Ender]

ChiefKiasu:

Ender:

If there's no gravity , out in space. Your fart will definitely push you in the opposite direction without stopping. You be lost in space. Like what they show in the movie Gravity and The Martian. Little burst of air will propel the astronaut in one direction.

:rotflmao: While I'll accept your theory, in reality, if you fart in space, you will only be doing it within your space suit, which will act to counter the force. So other than the inconvenience of cohabiting with your own stink, I seriously doubt it will make you fly off to the end of space...

PS. Matt Damon is my hero!

:lol:

[mum02]

4_my_son:

It is not just scratches.. Hard tyres wear down slower... it is an advantage in race with few pit stops.

I have not seen the actual queation but infer from the key words given as posted in this forum. The key words are old tyres, racing and the properties of such tyres..
I find strong acceptable... But if it is alluding to old tyres and in racing, then my choice is hard and flexible.

I undstd the qn is re putting tyres by side of the track to cushion impact of collision if any. I am not sure if I undstd correctly. Anyway teacher did say strong n fleck is correct.

[Kee Kor]

Personally I would choose strong and flexible but DS chose strong and smooth b'cos he said the question mentioned worn-off tires :scared: jialat

[4_my_son]

If it is used as shock absorber, then answer is strong and flexible.

[ilovelaksa]

So interesting. Dd2 class whatsapp grp had more than 1000 msgs ystd. Will be higher today aft HMT. Prior to that, ZERO. Mostly about meetg up to play sports, making crafts, thoughts about tv programmes, going for outings with family etc. One boy has even volunteered to tutor his younger sibling for SA2.

Ah life for our young 'uns shld be like this, building relationships, new experiences.
Dd2 is so excited! Still got HMT paper today.