# Circular motion, forcesWatch

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#1
I’m stuck on an Isaac physics question, I’ve tried this a couple times and keep getting the same answer. Attachment 879902

My working out is here, Attachment 879904

Also I have watched the hint video and they got a different equation when equating the vertical forces. I have Ncos(30) + mu*Nsin(30) = mg, but they have -mu *Nsin(30). On the diagram they have also drawn the friction force down the slope, but surely it should be up the slope? Super confused. Would appreciate help.

Also here is an image of the hint with a diagram and their starting equations. Attachment 879906
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1 week ago
#2
(Original post by Maximus 190)
I’m stuck on an Isaac physics question, I’ve tried this a couple times and keep getting the same answer. Attachment 879902

My working out is here, Attachment 879904

Also I have watched the hint video and they got a different equation when equating the vertical forces. I have Ncos(30) + mu*Nsin(30) = mg, but they have -mu *Nsin(30). On the diagram they have also drawn the friction force down the slope, but surely it should be up the slope? Super confused. Would appreciate help.

Also here is an image of the hint with a diagram and their starting equations. Attachment 879906
There is nothing attached.
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1 week ago
#3
(Original post by Maximus 190)
...
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#4
(Original post by ghostwalker)

https://imgur.com/a/i78v1ZY
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1 week ago
#5
Question asks for the maximum speed. I.e. if it went any faster the car would not make it round the curve. So friction is acting, in general, towards the centre of rotation, and hence down the slope.
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#6
(Original post by ghostwalker)
Question asks for the maximum speed. I.e. if it went any faster the car would not make it round the curve. So friction is acting, in general, towards the centre of rotation, and hence down the slope.
Oh right okay, I’ll try it again in a little bit. Thanks
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#7
(Original post by ghostwalker)
Question asks for the maximum speed. I.e. if it went any faster the car would not make it round the curve. So friction is acting, in general, towards the centre of rotation, and hence down the slope.
Tried that, now I’m just getting the same final equation but negative mu * sin 30 on the bottom. This gives me a negative value for the velocity squared?
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#8
(Original post by Maximus 190)
Tried that, now I’m just getting the same final equation but negative mu * sin 30 on the bottom. This gives me a negative value for the velocity squared?
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1 week ago
#9
(Original post by Maximus 190)
Tried that, now I’m just getting the same final equation but negative mu * sin 30 on the bottom. This gives me a negative value for the velocity squared?
At a guess you only changed one of your intial equations, but I've no idea as you haven't posted any working!
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#10
(Original post by ghostwalker)
At a guess you only changed one of your intial equations, but I've no idea as you haven't posted any working!
Do you see my working out now? I can upload to another site and link if not. I have the sane equations as the hint video now
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1 week ago
#11
(Original post by Maximus 190)
Do you see my working out now? I can upload to another site and link if not. I have the sane equations as the hint video now
Can see it now. cos30-mu sin 30 is still postive, giving a positive v^2. Does it not?
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#12
(Original post by ghostwalker)
Can see it now. cos30-mu sin 30 is still postive, giving a positive v^2. Does it not?
Ohhh I’m in radians, one second ffs lol
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#13
(Original post by ghostwalker)
Can see it now. cos30-mu sin 30 is still postive, giving a positive v^2. Does it not?
Yeah that worked, thanks!
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1 week ago
#14
(Original post by Maximus 190)
Classic! One thing to watch out for in exams, where you might have some questions in degrees and others in radians.
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