Login | Register

Welcome, Guest. Please login or register.

July 08, 2020, 01:24:37 pm

Author Topic: VCE Physics Question Thread!  (Read 306633 times)  Share 

0 Members and 2 Guests are viewing this topic.

lzxnl

  • Victorian
  • ATAR Notes Legend
  • *******
  • Posts: 3430
  • Respect: +210
Re: VCE Physics Question Thread!
« Reply #60 on: June 29, 2013, 03:13:09 pm »
+1
It depends on how the angle is defined. The formula is only used when the angle is measured between the heads of the vectors r and F (it's a vector equation). In this case, 60 degrees is the angle between the ladder and the horizontal, while here theta is the angle between r and mg, in this case the ladder and the VERTICAL.

This is why I like thinking that torque = moment arm * force where the moment arm is the component of the radius that is perpendicular to the force. You'll never get it wrong this way.
2012
Mathematical Methods (50) Chinese SL (45~52)

2013
English Language (50) Chemistry (50) Specialist Mathematics (49~54.9) Physics (49) UMEP Physics (96%) ATAR 99.95

2014-2016: University of Melbourne, Bachelor of Science, Diploma in Mathematical Sciences (Applied Maths)

2017-2018: Master of Science (Applied Mathematics)

2019-: ???

Accepting students for  VCE tutoring in Maths Methods, Specialist Maths and Physics! PM for more details

Homer

  • Victorian
  • Forum Obsessive
  • ***
  • Posts: 431
  • Respect: +10
Re: VCE Physics Question Thread!
« Reply #61 on: July 02, 2013, 11:41:55 am »
+1
The young's modulus for a rope of length 30m, cross-sectional area 30cm2, which stretches 2m under a load of 1000N is? ANS: 5 x 10^6 Nm-2

edit: accidentally clicked modify instead of quote, my bad (2/cos(c))
« Last Edit: July 02, 2013, 05:00:14 pm by 2/cos(c) »
Bachelor of Laws/Engineering

2013 ATAR: 98.65

Specialist Maths [53.06] Maths Methods [48.83] Physics [48.22]

Donuts. Is there anything they can't do?

sin0001

  • Victorian
  • Forum Obsessive
  • ***
  • Posts: 487
  • Respect: +1
  • School Grad Year: 2013
Re: VCE Physics Question Thread!
« Reply #62 on: July 02, 2013, 11:57:53 am »
0
It depends on how the angle is defined. The formula is only used when the angle is measured between the heads of the vectors r and F (it's a vector equation). In this case, 60 degrees is the angle between the ladder and the horizontal, while here theta is the angle between r and mg, in this case the ladder and the VERTICAL.
Is the torque formula examinable material for our core topics, or is it only required for a particular detailed study because I haven't seen it in the Heinemann textbook :/
Also, are you guys gonna reinforce the Unit 3 knowledge-through some mid-year exams- or continue on with the course, as revision?
ATAR: 99.00
Monash Commerce Scholars

Phy124

  • Honorary Moderator
  • Part of the furniture
  • *******
  • Posts: 1355
  • Respect: +464
Re: VCE Physics Question Thread!
« Reply #63 on: July 02, 2013, 04:59:53 pm »
0
The young's modulus for a rope of length 30m, cross-sectional area 30cm2, which stretches 2m under a load of 1000N is? ANS: 5 x 10^6 Nm-2

edit: accidentally clicked modify instead of quote, my bad (2/cos(c))









Is the torque formula examinable material for our core topics, or is it only required for a particular detailed study because I haven't seen it in the Heinemann textbook :/
Also, are you guys gonna reinforce the Unit 3 knowledge-through some mid-year exams- or continue on with the course, as revision?

I would think that torque is only relevant to the "Materials and their use in structures" detailed study.

Although your question wasn't directed at me, I would advise you to do some mid-year practice exams during these holidays to both reinforce key concepts and get a feel for VCAA physics exams.

edit: added answer to sin0001's question.
« Last Edit: July 02, 2013, 10:21:51 pm by 2/cos(c) »
2011
Mathematical Methods | Physics | Chemistry | English | Business Management

2012-2017
Bachelor of Science in Applied Mathematics and Bachelor of Civil Engineering (Honours) @ Monash University

Current
Transport Modeller @ Arup

Homer

  • Victorian
  • Forum Obsessive
  • ***
  • Posts: 431
  • Respect: +10
Re: VCE Physics Question Thread!
« Reply #64 on: July 03, 2013, 10:11:24 am »
+1




hey just a question why is it 0.003 wouldnt it be so  ?
 
Bachelor of Laws/Engineering

2013 ATAR: 98.65

Specialist Maths [53.06] Maths Methods [48.83] Physics [48.22]

Donuts. Is there anything they can't do?

Homer

  • Victorian
  • Forum Obsessive
  • ***
  • Posts: 431
  • Respect: +10
Re: VCE Physics Question Thread!
« Reply #65 on: July 03, 2013, 11:45:34 am »
+1
Also, What would be the tension in the cables of the cranes? Thankyou
Bachelor of Laws/Engineering

2013 ATAR: 98.65

Specialist Maths [53.06] Maths Methods [48.83] Physics [48.22]

Donuts. Is there anything they can't do?

Alwin

  • Victorian
  • Forum Leader
  • ****
  • Posts: 838
  • Respect: +241
Re: VCE Physics Question Thread!
« Reply #66 on: July 03, 2013, 12:58:15 pm »
0
Also, What would be the tension in the cables of the cranes? Thankyou

Let the tensions of the cables be T1 and T2, corresponding the the crane numbers Crane 1 and Crane 2.
Note I have included units in my working, just a small personal habit.

Using Crane 2 as the pivot,



You can now either say,


or use Crane 1 as a pivot,


Either way, it works out that


So, then tensions on cables of the cranes 1 and 2 are 2,400,000N an 600,000N in that order





hey just a question why is it 0.003 wouldnt it be so  ?

30cm2 is not the same as 30cm x 30cm = (0.3m)^2 = 0.09 m2

30cm2 is the same as 30cm x 1cm = (0.3m) x (0.01m) = 0.003 m2

The general rule is that 1cm2 = 0.0001m2


EDIT: answered both of homer's questions, rather than double post
« Last Edit: July 03, 2013, 01:08:24 pm by Alwin »
2012:  Methods [48] Physics [49]
2013:  English [40] (oops) Chemistry [46] Spesh [42] Indo SL [34] Uni Maths: Melb UMEP [4.5] Monash MUEP [just for a bit of fun]
2014:  BAeroEng/BComm

A pessimist says a glass is half empty, an optimist says a glass is half full.
An engineer says the glass has a safety factor of 2.0

Homer

  • Victorian
  • Forum Obsessive
  • ***
  • Posts: 431
  • Respect: +10
Re: VCE Physics Question Thread!
« Reply #67 on: July 05, 2013, 02:05:26 pm »
+1
Having trouble with 3. I dont know what they are asking for and how to work it out. :(
Bachelor of Laws/Engineering

2013 ATAR: 98.65

Specialist Maths [53.06] Maths Methods [48.83] Physics [48.22]

Donuts. Is there anything they can't do?

SocialRhubarb

  • Victorian
  • Forum Obsessive
  • ***
  • Posts: 313
  • Respect: +34
  • School Grad Year: 2013
Re: VCE Physics Question Thread!
« Reply #68 on: July 05, 2013, 03:00:17 pm »
0
They've given you a compass on the side, and the earth's magnetic field generally speaking runs south to north. Near the poles it's actually more into the ground, but usually it's mostly running south to north. Using right hand rule, if magnetic field is running from south to north, and current is going into the page, the field must be towards the right, or towards B.
Fight me.

Nato

  • Victorian
  • Trendsetter
  • **
  • Posts: 195
  • Respect: 0
Re: VCE Physics Question Thread!
« Reply #69 on: July 06, 2013, 11:16:12 pm »
0
Hey guys,

i am having a little trouble getting my head around Newton's third law. so it's the whole equal and opposite reaction thing.
so if an object exerts a force on the another, that object while exert the same force of same magnitude in the opposite direct. what i don't understand is how object are still able to move (i understand how the forces are acting on different and can't be cancelled out).

for example if you kick a ball with 100N, the ball exerts 100N back on you. Where does that *extra* force to make the ball go flying??


thank you guys
Class of 2014.

sin0001

  • Victorian
  • Forum Obsessive
  • ***
  • Posts: 487
  • Respect: +1
  • School Grad Year: 2013
Re: VCE Physics Question Thread!
« Reply #70 on: July 07, 2013, 12:09:18 am »
+1
Hey guys,

i am having a little trouble getting my head around Newton's third law. so it's the whole equal and opposite reaction thing.
so if an object exerts a force on the another, that object while exert the same force of same magnitude in the opposite direct. what i don't understand is how object are still able to move (i understand how the forces are acting on different and can't be cancelled out).

for example if you kick a ball with 100N, the ball exerts 100N back on you. Where does that *extra* force to make the ball go flying??


thank you guys
Okay so the forces are identical, but what is the difference here? Something has to be different between you and the ball, because clearly one is moving while the other is stable. The difference is mass; you weigh a lot more than the ball you've kicked and according to the formula: a = F/m, you are going to experience negligible acceleration while the ball is going to experience much greater acceleration, because if 'm' increases, then acceleration of an object will decrease. Therefore, you are going to 'absorb' a reaction force of 100 N by only experiencing negligible acceleration, but this force will cause the ball to go 'flying'.
Hope it made sense!
ATAR: 99.00
Monash Commerce Scholars

SocialRhubarb

  • Victorian
  • Forum Obsessive
  • ***
  • Posts: 313
  • Respect: +34
  • School Grad Year: 2013
Re: VCE Physics Question Thread!
« Reply #71 on: July 07, 2013, 05:30:34 pm »
0
You exert a force on the ball of 100N. The 'reaction force' which Newton's third law talks about is the ball's force applied to you. That force doesn't affect the ball's acceleration at all, because it doesn't act on the ball. It acts on you. So the original 100N of force which you apply isn't cancelled out by the reaction force from the ball because they act on different objects.
« Last Edit: July 07, 2013, 11:16:08 pm by SocialRhubarb »
Fight me.

Homer

  • Victorian
  • Forum Obsessive
  • ***
  • Posts: 431
  • Respect: +10
Re: VCE Physics Question Thread!
« Reply #72 on: July 08, 2013, 02:45:18 pm »
+1
What would be the direction of the magnetic force and how do we work it out?
Bachelor of Laws/Engineering

2013 ATAR: 98.65

Specialist Maths [53.06] Maths Methods [48.83] Physics [48.22]

Donuts. Is there anything they can't do?

jssantucci

  • Victorian
  • Fresh Poster
  • *
  • Posts: 3
  • Respect: 0
  • School: Melbourne Grammar School
Re: VCE Physics Question Thread!
« Reply #73 on: July 08, 2013, 03:58:21 pm »
0
Could someone please explain why when the secondary coil in a transformer is connected to a circuit with an open switch (i.e. one with no load) the energy used by the primary coil is zero? Wouldn't the power being dissipated by the primary coil always just be IxV regardless of what's going on in the secondary circuit? This is in relation to question 9 of chapter 10.6 in Heinemann.

Thanks

SocialRhubarb

  • Victorian
  • Forum Obsessive
  • ***
  • Posts: 313
  • Respect: +34
  • School Grad Year: 2013
Re: VCE Physics Question Thread!
« Reply #74 on: July 08, 2013, 05:07:45 pm »
0
Unfortunately I don't really understand the physics behind this but at the very least I can show you with the formulas.

Let the primary current be , the secondary current be, the turns on the primary coil be and the turns on the secondary coil be .

We know that , because the resistance across an open circuit is infinite, and .

We also know that .

Therefore, .

Thus, since and , the power dissipated in the primary circuit must be 0.

Like I said before, I don't actually understand the physics behind this, but somehow the secondary circuit must somehow influence the primary circuit? Maybe someone else can help with that.
Fight me.