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Physics Forces question

http://fcis.aisdhaka.org/personal/chendricks/IB/IB%20Exams/Phys05N/Physics%20HL%20paper%201.pdf



Question 16
Reply 1
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123chem
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17

This one is annoying too. Thanks in advance.
Original post by 123chem


The answer is D, reaction for is always perpendicular tot he surface, regardless.
Original post by 123chem

This one is annoying too. Thanks in advance.


B, acceleration of free fall is always 9.81 regardless of the mass of an object, in this case they just round 9.81 to 10ms-2. They try to trick you but must remember change from potential to kinetic and acceleration due to free fall are not dependent on the mass of an object.

For example if two people jumped out of a plane and they have different masses they would reach the bottom at the same time and the same speed
Original post by Konanabanana
B, acceleration of free fall is always 9.81 regardless of the mass of an object, in this case they just round 9.81 to 10ms-2. They try to trick you but must remember change from potential to kinetic and acceleration due to free fall are not dependent on the mass of an object.

For example if two people jumped out of a plane and they have different masses they would reach the bottom at the same time and the same speed


I thought it was A

wouldn't the masses act like this; https://youtu.be/eCMmmEEyOO0?t=39s ??

ie the top one falls at 9,81ms-2 and the bottom one doesn't move :dontknow:

Spoiler

Original post by DylanJ42
I thought it was A

wouldn't the masses act like this; https://youtu.be/eCMmmEEyOO0?t=39s ??

ie the top one falls at 9,81ms-2 and the bottom one doesn't move :dontknow:

Spoiler



Well the spring in that video only shows that sort of movement because the spring is plasticly deformed and wants to return to its original position, so in this case there is an extra force, tension, acting downwards for the top of the spring but not the bottom. However, in the question this is a piece of string not a spring which does not show any plastic/ elastic deformation so it is not necessarily trying to return to its original position so i would still go with B as the downward forces are the same for both.

I'm sure the person has the answers to the questions he is attempting because there would be no point otherwise.
Original post by Konanabanana
Well the spring in that video only shows that sort of movement because the spring is plasticly deformed and wants to return to its original position, so in this case there is an extra force, tension, acting downwards for the top of the spring but not the bottom. However, in the question this is a piece of string not a spring which does not show any plastic/ elastic deformation so it is not necessarily trying to return to its original position so i would still go with B as the downward forces are the same for both.

I'm sure the person has the answers to the questions he is attempting because there would be no point otherwise.


ah okay that kind of makes sense :laugh:, I didn't want to answer OP directly as I really wasn't sure

(I will stick to pure and stats i think)
Original post by DylanJ42
ah okay that kind of makes sense :laugh:, I didn't want to answer OP directly as I really wasn't sure

(I will stick to pure and stats i think)


aha, i don't even do maths i just do physics and well physics answers all concepts.
Maths is nothing without physics :biggrin:
Original post by Konanabanana
aha, i don't even do maths i just do physics and well physics answers all concepts.
Maths is nothing without physics :biggrin:


The sooner I can finish with resolving forces, projectiles etc the better, its just not something that comes naturally to me :frown:
Original post by DylanJ42
The sooner I can finish with resolving forces, projectiles etc the better, its just not something that comes naturally to me :frown:


xD good luck with it though
Reply 10
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123chem
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For the second one , according to markscheme our teacher gave, answer was D
Reply 11
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123chem
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Original post by Konanabanana
The answer is D, reaction for is always perpendicular tot he surface, regardless.



To that, the answer was A....i thought it would be D too
Reply 12
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1655957
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Original post by 123chem


The answer to 16 is A, we have only recently done this in Physics, it is perpendicular to the force provided by the tension in the wire, not the weight of the horizontal bare

EDIT: I didn't notice the above posting before I posted my input, sorry!
Reply 13
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123chem
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Original post by jakepds
The answer to 16 is A, we have only recently done this in Physics, it is perpendicular to the force provided by the tension in the wire, not the weight of the horizontal bare

EDIT: I didn't notice the above posting before I posted my input, sorry!



I still dont quite get it. What's the opposite force for reaction force in the diagram? As i see it, the tension is keeping it up and the weight keeping it down. Is the reaction force to oppose the horizontal force from the tension?
Definately A
I've done an AQA question like this
Reply 15
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123chem
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I know the first one is A, but why? And what about the second one?
Reply 16
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1655957
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Original post by 123chem
I know the first one is A, but why? And what about the second one?


When you say second one, do you mean question 2?
Reply 17
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123chem
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Original post by jakepds
When you say second one, do you mean question 2?


Yes
Reply 18
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1655957
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Original post by 123chem
Yes


It's ampere, that's just knowledge that you have to learn.
If you look up fundamental SI units, it will make more sense. I think they are units from which anything can be devised from?
Reply 19
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123chem
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Original post by jakepds
It's ampere, that's just knowledge that you have to learn.
If you look up fundamental SI units, it will make more sense. I think they are units from which anything can be devised from?


I meant second question in topic, not in the link. Apologies,

See second post

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