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Higher Physics 2013-2014

Sup guys.

Thought I'd start the thread early as I am crashing the course this year and could really use some help and advice from some fellow physicist !!

I've got a question that's for a homework which is due for tomorrow ;

The detector is now used at the same depth in fresh water. How would this affect the value of the buoyancy force? Justify your answer.

Density of fresh water = 1.00x10^3 kgm^-3
Density of salt water = 1.02x10^3 kgm^-3

Thanks !

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Reply 1
I think the more dense something is the greater the bouncy force is. ( could be wrong ):tongue:


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Reply 2
Original post by itsGrand131415
Sup guys.

Thought I'd start the thread early as I am crashing the course this year and could really use some help and advice from some fellow physicist !!

I've got a question that's for a homework which is due for tomorrow ;

The detector is now used at the same depth in fresh water. How would this affect the value of the buoyancy force? Justify your answer.

Density of fresh water = 1.00x10^3 kgm^-3
Density of salt water = 1.02x10^3 kgm^-3

Thanks !


What was the first part of the question?

I did higher physics (A1) and I am doing advance higher this year so will try and help through the year if I can.
Reply 3
I got a couple of questions about vectors homework.. I wasn't in class to do it so I'm quite confused to say the least :tongue:

1) A ferry crosses a river that is flowing at 5ms. If the ferry is travelling at 12ms, calculate its resultant velocity.

I got 13ms, but I'm unsure what I was meant to do so I just played about with the numbers :tongue:

2) A footballer runs around a football pitch as part of his training. He starts at the halfway line and runs around the pitch to point D (basically, he runs right round the pitch and stops at the corner before completing a full lap, if that makes any sense). This run takes him 50 seconds.

a) Calculate the total distances travelled by the footballer (basically runs 50m to one corner from halfway, then 70m upwards to the next corner, 100m across the pitch to next corner then down 70m to point D at next corner) - I basically added them up and got 290m.
b) What is his final displacement at point D - I just put 50m, as I'm not sure what that means but I thought it meant how much did he still have to complete? I may be completely wrong :lol:
c) This is the part I'm stuck on. Calculate the footballer's average velocity for the run. I have absolutely no clue what to do or where to start :tongue: So any help would be appreciated :smile:
c) Calculate the footballer's average velocity for the run.
Original post by CSM1996
I got a couple of questions about vectors homework.. I wasn't in class to do it so I'm quite confused to say the least :tongue:

1) A ferry crosses a river that is flowing at 5ms. If the ferry is travelling at 12ms, calculate its resultant velocity.

I got 13ms, but I'm unsure what I was meant to do so I just played about with the numbers :tongue:

2) A footballer runs around a football pitch as part of his training. He starts at the halfway line and runs around the pitch to point D (basically, he runs right round the pitch and stops at the corner before completing a full lap, if that makes any sense). This run takes him 50 seconds.

a) Calculate the total distances travelled by the footballer (basically runs 50m to one corner from halfway, then 70m upwards to the next corner, 100m across the pitch to next corner then down 70m to point D at next corner) - I basically added them up and got 290m.
b) What is his final displacement at point D - I just put 50m, as I'm not sure what that means but I thought it meant how much did he still have to complete? I may be completely wrong :lol:
c) This is the part I'm stuck on. Calculate the footballer's average velocity for the run. I have absolutely no clue what to do or where to start :tongue: So any help would be appreciated :smile:
c) Calculate the footballer's average velocity for the run.


B) displacement is the distance as the crow flies. I.E from start to finish in the shortest route possible. Since it is a vector you need to also have a bearing from the start point to the end point. (i suggest using scale drawing to find this)

C) velocity is displacement over time :smile:

Sorry i couldnt give you answers, I cant visualise what you said xD
hopefully i have explained this clearly enough :tongue:
Reply 5
Could someone please explain to me how you calculate a bearing in a vectors question?
Reply 6
Original post by Pennyarcade
B) displacement is the distance as the crow flies. I.E from start to finish in the shortest route possible. Since it is a vector you need to also have a bearing from the start point to the end point. (i suggest using scale drawing to find this)

C) velocity is displacement over time :smile:

Sorry i couldnt give you answers, I cant visualise what you said xD
hopefully i have explained this clearly enough :tongue:


For B I think it's meant to be at a right angle (or at least the wee picture looks it :lol:)

And thanks yeah, I managed to get it from the equation! Haha my explanation wasn't the best sorry!
Reply 7
I did Higher, Advanced Higher and Im going into a Physics degree, so Im good to be asked questions.

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Original post by Don'tKnow!
Could someone please explain to me how you calculate a bearing in a vectors question?



Use scale drawing. For example if a question was from 2012:

Cyclist X travels 12km due East (bearing 090). He then turns onto a bearing
of 200 (20° West of South) and travels a further 15km to arrive at B. He takes
1 hour 15 minutes to travel from A to B.

Use scale drawing: Measure 090 east using a protractor and draw a 12 cm line (1cm=1km). Then measure 200 FROM THE NORTH using the protractor and make a mark, then draw a 15 cm line. This will leave you with two lines drawn. Then make a line from A to B (this will be your displacement). Now using your protractor, measure the bearing FROM THE NORTH, then simply count the degrees until you reach the displacement line and viola you have your bearing.
http://www.youtube.com/watch?v=-NbQjliNkhc

Just thought id share this video series, as well as being pretty funny they really help with higher physics!
We had a surprise vector test today. It didn't to too good... Oh well :tongue:

I don't really get what's the point in the scale diagrams. I never know what scale to choose.
My diagrams are either too small to be accurate or too big to fit on the page. Why can't we just use Pythagoras?
Original post by Nessie162
We had a surprise vector test today. It didn't to too good... Oh well :tongue:

I don't really get what's the point in the scale diagrams. I never know what scale to choose.
My diagrams are either too small to be accurate or too big to fit on the page. Why can't we just use Pythagoras?


I thought the exact same as you until recently when I was doing a homework question and I realised how much easier scale diagrams are.
You can use the cosine rule, sine rule and pythagoras if you want, but you need to be brilliant at maths (which Im not) and be able to know what angles to use etc. Plus most vector diagrams arent right angled, so pythagoras wont work. Also, you dont need to get the exact answer if you use scale diagrams which helps :tongue:
Higher Physics shall be interesting this year!!!
Woo! All the Physicists have gathered, and it shall be wonderful! Only just started Unit 1 proper, after finishing up the practical work and the Uncertainties sub-topic. I'm very confused at the moment, but I'm going to try and figure everything out this weekend with the assistance of my good friends Bitesize, Leckie&Leckie and How to Pass :smile:
Our class has done the uncertainities section and we're doing work on vectors, scalars, equations of motions etc.
There are 17 people in my class, 12 are boys who clearly don't like physics or care about doing well. We've basically repeated everything we did in June because they kept answering questions wrong. -.- I don't think the teacher can be that terrible though because there's enough for an AH class.
For some reason, he has an aversion to helping me though. For standard grade, I literally had my hand up for ten minutes before he helped me. He even looked up, saw me and just continued with what he was doing. Then as soon as someone else needed help, he answered them then felt he had no choice but to help me. I could do the work in half the time if he wasn't so slow -.-
I wouldn't care if he was helping other people at the time but it was the fact he wasn't doing
anything, and he even achknowledged the fact I clearly needed help and still ignored me.
I'll be relying on the internet this year.
Can anyone please help me with C? I have a slight idea how to do it, but i want to be 100% sure :tongue:

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Original post by Pennyarcade
Can anyone please help me with C? I have a slight idea how to do it, but i want to be 100% sure :tongue:

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Using UVAST, the vertical displacement = 0. Using your equations of motion, you can calculate the time. Which can be used with your horizontal velocity to calculate the horizontal displacement :smile:
Original post by TheFOMaster
Using UVAST, the vertical displacement = 0. Using your equations of motion, you can calculate the time. Which can be used with your horizontal velocity to calculate the horizontal displacement :smile:


I was thinking along those lines :smile:, Thanks alot! This will be the first of many questions unfortunately...

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Reply 18
We're onto the graph questions and we just finished equations of motion. The teacher said we'll be moving 4 weeks faster than the past 2 years he's taught it though... Not looking forward to that.
Original post by Pennyarcade
I was thinking along those lines :smile:, Thanks alot! This will be the first of many questions unfortunately...

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Nae Bor. If you need help just post and someone will get ya :smile:

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