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Any science students or teachers...help please?

Goofeys Girl Avatar
6y, 8m agoPosted 6 years, 8 months ago
Hi
This sounds daft but my son has had a test on moments in science.....to do with pressure.
The question he had at age 14 showed a child on a see saw on the left end and nobody on the other and the question said what force is being applied;
Well sounds obvious but most kids put simply DOWN as the answer.
My son had read a revision book and this book showed exactly the same sort of see saw and said it was an anticlockwise moment...
So thats what he put but his teacher said its wrong and should just have been Down.
Anybody know if my son was right or wrong.
Not really too bothered as it was a little test but the problem i now have is he says he is never going to look at revision books again as they give wrong answers. We have only just tried to get him to read round subjects and this has thrown everything in the air. If someone can say either he is right or that he is wrong and misunderstood the revision book i would appreciate it.
Goofeys Girl Avatar
6y, 8m agoPosted 6 years, 8 months ago
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banned#1
Gravity and the boys weight in relation to it
banned 1 Like #2
Anticlockwise may have been correct if there was no floor - however, I presume there was some ground in the image? Therefore, by interpretation, down would also be correct.

Although I would have thought gravity would have been a smarter answer.
1 Like #3
The problem i now have is he says he is never going to look at revision books again as they give wrong answers.


Classic, I remember using this one.

Down is right, anti-clockwise is wrong
banned#4
The revision book was correct it would have been an anti clockwise movement around the axle of the see saw but the question was what force was being applied, in which case its a downward force which is cause by gravity and the weight of the boy.

I used to hate it when questions are asked akwardly, teachers seem to think its a great idea to do it for some reason.
1 Like #5
A moment is a turning effect so may be clockwise or anticlockwise, however it seems the question was what force was applied and it seems a downward force was applied.
#6
Just shows you they are taught differently today....gravity sounds great but isnt even mentioned in either his text or revision book.....and at 14 down seems abit easy....Lol you probably get a GCSE for that.
Thanks
#7
CFC_Mark
Classic, I remember using this one.

Down is right, anti-clockwise is wrong


It looks like the revision book is wrong then...as it clearly says that the see saw has an anti clockwise momement...good old letts.

How i get him to keep revising now will be the fun part.
#8
Paddy Charlie
The revision book was correct it would have been an anti clockwise movement around the axle of the see saw but the question was what force was being applied, in which case its a downward force which is cause by gravity and the weight of the boy.

I used to hate it when questions are asked akwardly, teachers seem to think its a great idea to do it for some reason.


Bet you are right...he cant remember exactly how it was worded....thanks for that...at least he will understand his mistake now and needs to be careful with how the question is worded.

Thanks everyone Paddy Charlie looks to have solved the problem...and i can now explain it to my son...cheers.

Repped you all....appreciate your answers
banned 1 Like #9
Goofeys Girl
It looks like the revision book is wrong then...as it clearly says that the see saw has an anti clockwise momement....


The key is in the wording, as the question asked what force was applied
#10
The force is the person's weight, which is their mass affected by gravity.
W=mg
where g is acceleration due to gravity.

E.g, if the person's mass is 50kg, their weight = 50kg x 9.81ms-2= 491 N

(The units of force are Newtons (N))

Hope this helps.
:)
#11
I would say that down is incorrect too, as its actually (as already stated) gravitatiional pull towards the earth this in terms of the universe is not down.
#12
Alfonse;8236854
I would say that down is incorrect too, as its actually (as already stated) gravitatiional pull towards the earth this in terms of the universe is not down.

Gravity

All objects have a force that attracts them towards each other. This is called gravity. Even you attract other objects to you because of gravity, but you have too little mass for the force to be very strong.
Gravitational force increases when: [LIST]
[*]the masses are bigger
[*]the objects are closer[/LIST]Gravity only becomes noticeable when there is a really massive object like a moon, planet or star. We are pulled down towards the ground because of gravity. The gravitational force pulls in the direction towards the centre of the Earth.
http://www.bbc.co.uk/schools/ks3bitesize/science/images/gravity.gif
"Down" is towards the centre of the Earth, wherever you are on the planet

http://www.bbc.co.uk/schools/ks3bitesize/science/energy_electricity_forces/forces/revise3.shtml
#13
the moment is calculated by the mass in newtons multiplied by the distance from the point of rotation. so if the boy had a mass of 200N at a distance of 3m. the moment would be 600Nm. so if the question was what is the direction of the force, then you could say anticlockwise.

the question is "what force is being applied?" the answer should be a downward force,gravity. gravity pulls to the center of the earth.

moments are very complicated to understand. they are not to do with pressure but with forces. there is a difference.

misconceptions arise when the topic is not covered correctly or even when the teacher does not understand the topic themselves. it is completely possible for the teacher to be a biologist, being asked to teach physics.
#14
melipona
Gravity

All objects have a force that attracts them towards each other. This is called gravity. Even you attract other objects to you because of gravity, but you have too little mass for the force to be very strong.
Gravitational force increases when: [LIST]
[*]the masses are bigger
[*]the objects are closer[/LIST]Gravity only becomes noticeable when there is a really massive object like a moon, planet or star. We are pulled down towards the ground because of gravity. The gravitational force pulls in the direction towards the centre of the Earth.
http://www.bbc.co.uk/schools/ks3bitesize/science/images/gravity.gif
"Down" is towards the centre of the Earth, wherever you are on the planet

http://www.bbc.co.uk/schools/ks3bitesize/science/energy_electricity_forces/forces/revise3.shtml


for purpose of those GCSE exams it is, after that it isn't, my physics lecturer at Uni made us swear never to say it again

but meh
#15
I would go with gravity, or if you think they were asking for anti-clockwise go with that. But I wouldn't have put down, that would feel like taking the ****.
#16
[QUOTE=Benjimoron]I would go with gravity, or if you think they were asking for anti-clockwise go with that. But I wouldn't have put down, that would feel like taking the ****.[/QUOTE]

Yes at 14 years old you would hope they would want something more than DOWN.....
#17
Anti-clockwise moment IMO. If the see-saw was suspended in thin air (stay with me), then it would go round like clock hands. As it's a normal see-saw and therefore hits the ground, it's only a small turn (say 20 degrees) but it's still an anti-clockwise moment.

Down is over-simplifying it but sort of correct. Why say on the left hand side if they were just looking for "down"? At best it should have been downWARD pressure.

Your son has my sympathies, perhaps he should print off this discussion and take it to that egg of a teacher of his...
banned#18
tallpete33
Anti-clockwise moment IMO. If the see-saw was suspended in thin air (stay with me), then it would go round like clock hands. As it's a normal see-saw and therefore hits the ground, it's only a small turn (say 20 degrees) but it's still an anti-clockwise moment.

Down is over-simplifying it but sort of correct. Why say on the left hand side if they were just looking for "down"? At best it should have been downWARD pressure.

Your son has my sympathies, perhaps he should print off this discussion and take it to that egg of a teacher of his...


But then again, the FORCE is actually what the child is putting on the see saw regardless of what EFFECT this has on the seesaw.

So, in theory, the child is only putting downward force on the object. The object (by means of having a centre point) is then creating the anti clockwise effect.

We are missing the obvious answer of Upward by the way. I used to do that all the time. You launch yourself upward with nobody sitting on the other end, the other end hits the ground, you rise about ten inches up in the air, then hit the see-saw and then hit the ground with a thud.
Happy days.... :oops:
#19
tallpete33
Anti-clockwise moment IMO. If the see-saw was suspended in thin air (stay with me), then it would go round like clock hands. As it's a normal see-saw and therefore hits the ground, it's only a small turn (say 20 degrees) but it's still an anti-clockwise moment.

Down is over-simplifying it but sort of correct. Why say on the left hand side if they were just looking for "down"? At best it should have been downWARD pressure.

Your son has my sympathies, perhaps he should print off this discussion and take it to that egg of a teacher of his...


I like the idea of taking this in....although with a name like Goofeys Girl maybe not. Would be a bit embarrassing next parents evening.
#20
Think of a force as like a push or a pull. In this case, the weight of the child is pushing the see-saw down, therefore a downward force is the correct answer.
A moment is the rotational effect of a force around a fixed point, in this case the centre of the see-saw. It is calculated as the total force multiplied by the perpendicular distance from the fixed point.
It's all to do with mechanics...
#21
tallpete33
Anti-clockwise moment IMO. If the see-saw was suspended in thin air (stay with me), then it would go round like clock hands. As it's a normal see-saw and therefore hits the ground, it's only a small turn (say 20 degrees) but it's still an anti-clockwise moment.

Down is over-simplifying it but sort of correct. Why say on the left hand side if they were just looking for "down"? At best it should have been downWARD pressure.

Your son has my sympathies, perhaps he should print off this discussion and take it to that egg of a teacher of his...


The moment is "created" as a result of the downwards force. Think of the see-saw with no-one on it, it's in a state of equilibrium. You have to apply a force for it to rotate, thus creating the moment.
#22
http://www.bbc.co.uk/schools/ks3bitesize/science/images/weights_on_a_seesaw.gif

1. you need to take your son to the park.
2. he needs to draw the above diagram to answer the question.
1 Like #23
JonnyTwoToes
But then again, the FORCE is actually what the child is putting on the see saw regardless of what EFFECT this has on the seesaw.

So, in theory, the child is only putting downward force on the object. The object (by means of having a centre point) is then creating the anti clockwise effect.

We are missing the obvious answer of Upward by the way. I used to do that all the time. You launch yourself upward with nobody sitting on the other end, the other end hits the ground, you rise about ten inches up in the air, then hit the see-saw and then hit the ground with a thud.
Happy days.... :oops:


A moment is a turning force, which can be clockwise or anticlockwise :-D
1 Like #24
tallpete33
A moment is a turning force, which can be clockwise or anticlockwise :-D


A moment is the rotational effect of a force about a fixed point. I've got a fair idea what I'm talking about.

Btw, did you look at the link you provided? Specifically the bit that says that a moment = force x distance?
1 Like #25
I don't think moments are in the GCSE syllabus. I'm doing A level mechanics and never had to do moments at GCSE.

The Force being applied by the child is down. The moment is anticlockwise as the boy is sitting on the left. The force being applied and the moment are two completely different questions, so the revision guide is right in saying that the moment is anticlockwise. The question asked was about the force applied so the answer would be down.

HTH
1 Like #26
If only the answers had been so easy in my day, what direction is this child moving? down lol!!!

Followed by which direction is the sky? up!
1 Like #27
Down as in downwards is indeed correct.
as Down refers to anything towards the Earth's core (at GCSE level)

The question asks what force the CHILD is applying.
So gravity is incorrect, as gravity acts ON us, rather than us able to impart gravity.
Anticlockwise is also incorrect as moments are different to forces.

Although good intentioned, and an educated answer (obviously) your son is unfortunately incorrect.
HTH
#28
Spammed
I don't think moments are in the GCSE syllabus. I'm doing A level mechanics and never had to do moments at GCSE.

The Force being applied by the child is down. The moment is anticlockwise as the boy is sitting on the left. The force being applied and the moment are two completely different questions, so the revision guide is right in saying that the moment is anticlockwise. The question asked was about the force applied so the answer would be down.

HTH


Yes think thats exactly right, they were studying moments, he's at the end of key stage 3 but i agree with you in this question he should have put down. I think he needs to learn to read the questions a bit more carefully. Oh well roll on next year when he is hopefully doing triple science.
Thanks everyone it is amazing how people take time to answer on this site. I appreciate all your help. Rep left.
banned#29
what happens the moment the boy does a fart?
#30
bykergrove
what happens the moment the boy does a fart?


That would have the same effect as weeing in the sea - would make absolutely no difference to anything!!!!
banned#31
shibi din
That would have the same effect as weeing in the sea - would make absolutely no difference to anything!!!!


what if he lit it :p
#32
bykergrove
what if he lit it :p


upthrust. dependent on his diet he could end up in orbit. :thumbsup:

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