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Author Topic: Edexcel PHYSICS Doubts  (Read 137994 times)

Offline The Golden Girl =D

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Re: Edexcel PHYSICS Doubts
« Reply #375 on: January 06, 2011, 07:59:50 am »
sorry I meant are under graph is always taken FROM the X-axis !!!
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Offline Vin

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Re: Edexcel PHYSICS Doubts
« Reply #376 on: January 06, 2011, 02:16:45 pm »
Quote from: Vampire-Love4ever on January 04, 2011, 11:46:46 pm
How to do draw C?

[Attached]

Remember,

Young Modulus  = stress / strain

therefore, the gradient of the graph determines the young modulus.

The question says :
C has smaller modulus than A & B, so the gradient is the least/
C is stronger than A & B, so the maximum point of the graph (stress and strain) should be greater than A&B
C is a brittle substance, that means when crossed the limit of proportionality, the substance breaks, so the line C will have an abrupt end. (< This is the property of the graphs for brittle substances - remember it, it'll come in handy with other ques as well.
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Offline Vampire-Love4ever

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Re: Edexcel PHYSICS Doubts
« Reply #377 on: January 06, 2011, 03:01:20 pm »
Quote from: Vin on January 06, 2011, 02:16:45 pm
[Attached]

Remember,

Young Modulus  = stress / strain

therefore, the gradient of the graph determines the young modulus.

The question says :
C has smaller modulus than A & B, so the gradient is the least/
C is stronger than A & B, so the maximum point of the graph (stress and strain) should be greater than A&B
C is a brittle substance, that means when crossed the limit of proportionality, the substance breaks, so the line C will have an abrupt end. (< This is the property of the graphs for brittle substances - remember it, it'll come in handy with other ques as well.

Thank you.
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Offline Vampire-Love4ever

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Re: Edexcel PHYSICS Doubts
« Reply #378 on: January 08, 2011, 06:08:23 pm »
A horse pulls a barge of mass 5000kg along a canal using a rope 10m long.
The horse is attached to a point on the barge 2m from the bank. As the barge starts to move, the
tension in the rope is 500N. Calculate the barge's initial acceleration parallel to the bank.
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Offline astarmathsandphysics

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Re: Edexcel PHYSICS Doubts
« Reply #379 on: January 08, 2011, 07:52:56 pm »
here
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Offline Vampire-Love4ever

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Re: Edexcel PHYSICS Doubts
« Reply #380 on: January 08, 2011, 09:28:17 pm »
Material with the steepest graph will have the highest young modulus [stiffness]?

Is that right?

Please correct me if I am wrong.
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Offline astarmathsandphysics

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Re: Edexcel PHYSICS Doubts
« Reply #381 on: January 08, 2011, 09:29:42 pm »
Yes gradient is Young's modulus
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Offline Vampire-Love4ever

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Re: Edexcel PHYSICS Doubts
« Reply #382 on: January 08, 2011, 09:52:17 pm »
Quote from: astarmathsandphysics on January 08, 2011, 09:29:42 pm
Yes gradient is Young's modulus

Thank you for your help.
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Offline astarmathsandphysics

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Re: Edexcel PHYSICS Doubts
« Reply #383 on: January 08, 2011, 10:16:00 pm »
No probs. Always something going wrong.
Blogs dont work on freeexampapers/courseworkbak/astarmathsandphysics
theeducationchannel is down
astarmathsandphysics was hacked over xmas
On the other hand my server is fixed
So thats all right then
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Offline Vampire-Love4ever

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Re: Edexcel PHYSICS Doubts
« Reply #384 on: January 08, 2011, 10:56:30 pm »
Quote from: astarmathsandphysics on January 08, 2011, 10:16:00 pm
No probs. Always something going wrong.
Blogs dont work on freeexampapers/courseworkbak/astarmathsandphysics
theeducationchannel is down
astarmathsandphysics was hacked over xmas
On the other hand my server is fixed
So thats all right then


Hope everything gets better :)
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Offline Vampire-Love4ever

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Re: Edexcel PHYSICS Doubts
« Reply #385 on: January 08, 2011, 11:08:37 pm »
A car of mass 1000kg tows a caravan of mass 800kg. The driver wants to speed up with an
acceleration of 2ms^-2.
a-With what force must the car pull the caravan? What motive force must the
engine provide? [caravan has a drag force of 400N and the car has a drag force of 200N]
b- The engine of the car can provide a maximum motive force of 6000N. Assuming that the drag
forces are unchanged. Calculate the maximum acceleration which can be achieved?
c- The force which the car exerts on the caravan at this acceleration.





answers: a- 4200N, b- 3ms^-2 and c- 2800N.




Please explain how to do this question.
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Offline zetsuboushita

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Re: Edexcel PHYSICS Doubts
« Reply #386 on: January 09, 2011, 03:38:43 am »
a) consider this:-

a=2m/s^2,  (caravan 800kg)---(car 1000kg)---->Engine force
     400N<---                      200N<---

Resolve vertically,
Engine force -200-400=(1800)(2)
              Engine force=4200N

b)Given engine force = 6000N
Sub into above equation, 6000-200-400=(1800)(a)     
                                                    a=3 m/s^2

c) Consider caravan,
   a=3 m/s^2
400N<---(caravan 800kg)--->Tension of tow bar(i.e. force car acting on caravan)

Resolve vertically,
T-400=(800)(3)
      T=2800N
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Offline Vampire-Love4ever

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Re: Edexcel PHYSICS Doubts
« Reply #387 on: January 09, 2011, 12:15:12 pm »
Quote from: zetsuboushita on January 09, 2011, 03:38:43 am
a) consider this:-

a=2m/s^2,  (caravan 800kg)---(car 1000kg)---->Engine force
     400N<---                      200N<---

Resolve vertically,
Engine force -200-400=(1800)(2)
              Engine force=4200N

b)Given engine force = 6000N
Sub into above equation, 6000-200-400=(1800)(a)     
                                                    a=3 m/s^2

c) Consider caravan,
   a=3 m/s^2
400N<---(caravan 800kg)--->Tension of tow bar(i.e. force car acting on caravan)

Resolve vertically,
T-400=(800)(3)
      T=2800N

For part b- why dont we minus 6000 from 4200N?
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Offline Vampire-Love4ever

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Re: Edexcel PHYSICS Doubts
« Reply #388 on: January 09, 2011, 08:15:56 pm »
Q- Graph in the figure shows how the vertical component of the trajectory of a rocket varies with the time, t, from it's take-off on level ground to the highest point of it's trajectory.

Use the graph to estimate the maximum height reached by the rocket.





[please ignore the numbers in the image attached].
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Offline Vampire-Love4ever

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Re: Edexcel PHYSICS Doubts
« Reply #389 on: January 09, 2011, 08:20:20 pm »
A ball is dropped and rebounds vertically to a less than original height.



Please answer part c of the question.
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