m1 maths Watch

svirdi
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a particle moving on a smooth horizontal surface encounters two rough areas, each 10m wide. The coeff of friction for the two areas are 0.2 and 0.4 respectively. find the minimum initial speed of the particle if it just makes it across the two areas.

Please help

Step by step working would be great thanx
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Slowbro93
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(Original post by svirdi)
a particle moving on a smooth horizontal surface encounters two rough areas, each 10m wide. The coeff of friction for the two areas are 0.2 and 0.4 respectively. find the minimum initial speed of the particle if it just makes it across the two areas.

Please help

Step by step working would be great thanx
What have you done in terms of working out so far? Are the surfaces at an angle?
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davros
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(Original post by svirdi)
a particle moving on a smooth horizontal surface encounters two rough areas, each 10m wide. The coeff of friction for the two areas are 0.2 and 0.4 respectively. find the minimum initial speed of the particle if it just makes it across the two areas.

Please help

Step by step working would be great thanx
We're not going to do the problem for you!

Start by setting up some equations for the motion using an unknown variable u as your initial speed.
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lerjj
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(Original post by Doctor_Einstein)

Therefore .....? I'll leave the conclusion for you to finish as full solutions here are not permitted.
umm...
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Doctor_Einstein
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(Original post by lerjj)
umm...
Mate I'm sorry it's in the rules.
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Slowbro93
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(Original post by Doctor_Einstein)
Mate I'm sorry it's in the rules.
Yes, however we wanted to see the equations that he set up.
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lerjj
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(Original post by Doctor_Einstein)
Mate I'm sorry it's in the rules.
Was not saying umm... about the fact that you didn't quite post a full solution. Was umming about the fact that you did everything but.
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davros
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(Original post by Doctor_Einstein)
Force of friction = -uN, where u is coefficient of friction and N is normal force.

.
The OP is supposed to be doing this work, not you!

I'm not going to warn you again so I'll just report this post.
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svirdi
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I have never used this site before and only stumbled upon it by google search, also I do not have a maths tutor and I am doing this myself...so less of the grief
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Slowbro93
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(Original post by svirdi)
I have never used this site before and only stumbled upon it by google search, also I do not have a maths tutor and I am doing this myself...so less of the grief
We're not trying to give you grief :nah: However, by knowing if you've done any working it will help you in the long run as opposed to just giving you the answer
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Doctor_Einstein
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(Original post by Slowbro93)
We're not trying to give you grief :nah: However, by knowing if you've done any working it will help you in the long run as opposed to just giving you the answer
Actually giving him a clear detailed solution, where each line follows logically from the next will be of most benefit to him in the long run. As someone who has achieved the highest results in university physics and mathematics, I can vouch for this. Most of my successful colleagues agree, but many of my mediocre colleagues continue to spout the line that it is best for the student if they figure it out themselves. Direct instruction has proven time and again to be the most effective and efficient form of learning.
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Slowbro93
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(Original post by Doctor_Einstein)
Actually giving him a clear detailed solution, where each line follows logically from the next will be of most benefit to him in the long run. As someone who has achieved the highest results in university physics and mathematics, I can vouch for this. Most of my successful colleagues agree, but many of my mediocre colleagues continue to spout the line that it is best for the student if they figure it out themselves. Direct instruction has proven time and again to be the most effective and efficient form of learning.
Yes but as someone who achieved one of the highest marks in both my maths and physics modules in my degree, I can argue that for my friends who figured it out per say as opposed to getting detailed answers did much better. (And this is how I teach my students)

If you're not happy with this I would either:

1. Not bother as you're gonna get warned or
2. Have an actual discussion with th moderation team and providing evidence as to why your method could work

Bearing in mind that not everyone has "attempted" the question and providing an them with a detailed solution could essentially result in them having someone do their homework. And issue if they get to the exam and they have no idea as to how the method works.
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Doctor_Einstein
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(Original post by Slowbro93)
Yes but as someone who achieved one of the highest marks in both my maths and physics modules in my degree, I can argue that for my friends who figured it out per say as opposed to getting detailed answers did much better. (And this is how I teach my students)

If you're not happy with this I would either:

1. Not bother as you're gonna get warned or
2. Have an actual discussion with th moderation team and providing evidence as to why your method could work

Bearing in mind that not everyone has "attempted" the question and providing an them with a detailed solution could essentially result in them having someone do their homework. And issue if they get to the exam and they have no idea as to how the method works.
By going through a full solution it becomes self evidence how a particular method works, if each line follows logically from the next.
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Slowbro93
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(Original post by Doctor_Einstein)
By going through a full solution it becomes self evidence how a particular method works, if each line follows logically from the next.
We are going to have to agree to disagree. If you have an issue with the rules bring it up with the mods
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davros
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(Original post by svirdi)
I have never used this site before and only stumbled upon it by google search, also I do not have a maths tutor and I am doing this myself...so less of the grief
No-one is trying to give you grief!

For most students, an explanation given in the classroom followed by practice on worked examples in a textbook should be sufficient to get you started on things like this.

If your background or environment are different, it is helpful to everyone (including yourself) if you say so

So - what do you know already? Have you done GCSE maths before tackling this? Why are you studying this now - is it for an exam or just for self-interest?

Have you covered SUVAT equations and how to set them up? Do you know how to model friction, and how to calculate the frictional force during motion (when friction is limiting)?

Tell us what you've covered already and we can give you appropriate help
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svirdi
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(Original post by davros)
No-one is trying to give you grief!

For most students, an explanation given in the classroom followed by practice on worked examples in a textbook should be sufficient to get you started on things like this.

If your background or environment are different, it is helpful to everyone (including yourself) if you say so

So - what do you know already? Have you done GCSE maths before tackling this? Why are you studying this now - is it for an exam or just for self-interest?

Have you covered SUVAT equations and how to set them up? Do you know how to model friction, and how to calculate the frictional force during motion (when friction is limiting)?

Tell us what you've covered already and we can give you appropriate help

Yes I have a A* in GCSE maths. It is for an exam, and i'm doing well in the core books jus have the M books to finish.

Yes I have covered the SUVAT equations and know how to set them up. Don't know how to model friction but I am trying to set up the equations.

Sometimes when I read the questions it's obvious what I have to do and sometimes, I think I know what to do but other times I have no idea where to start - and on these questions I can spend all day on them but get no where and then I end up leaving questions out of chapters.

I will get there once I've practiced enough questions.

I have don:
Kinematics in one and two dimentions
Statics and forces
Newtons laws of motion - doing now

But I have left some questions out of topics etc. I don't expect people to teach me but to just help me understand the questions so they become obvious to me would be a great help
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Doctor_Einstein
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(Original post by svirdi)
Yes I have a A* in GCSE maths. It is for an exam, and i'm doing well in the core books jus have the M books to finish.

Yes I have covered the SUVAT equations and know how to set them up. Don't know how to model friction but I am trying to set up the equations.

Sometimes when I read the questions it's obvious what I have to do and sometimes, I think I know what to do but other times I have no idea where to start - and on these questions I can spend all day on them but get no where and then I end up leaving questions out of chapters.

I will get there once I've practiced enough questions.

I have don:
Kinematics in one and two dimentions
Statics and forces
Newtons laws of motion - doing now

But I have left some questions out of topics etc. I don't expect people to teach me but to just help me understand the questions so they become obvious to me would be a great help
Force of friction = -uN = -umg, where u is coefficient of friction.

Also Force = ma

So,

ma = -umg

a =-ug = -u*9.8

Thus the acceleration on the first surface is -0.2*9.8 and -0.4*9.8 on the second surface.

Since you know a for both surfaces, and you know final velocity for the second surface is 0, and displacement is 10, calculate the initial velocity for the second surface. Then use this initial velocity as the final velocity for the first surface and calculate initial velocity for the first surface.

Have a go and post your working.
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davros
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(Original post by svirdi)
Yes I have a A* in GCSE maths. It is for an exam, and i'm doing well in the core books jus have the M books to finish.

Yes I have covered the SUVAT equations and know how to set them up. Don't know how to model friction but I am trying to set up the equations.
In order to use the SUVAT equations you need constant acceleration. When you have motion against friction, the friction is what is called "limiting" and obeys the law F = \mu R where R is the normal reaction to the surface and \mu is the coefficient of friction.

In this case the normal reaction force R balances the weight mg so you get the equation that Doctor Einstein has given you.

Knowing F you can deduce the acceleration that applies to each part of the motion so you can start setting up your SUVAT equations.
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