# Centripetal force mcqWatch

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#1
Why is D??
Why not B?

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1 month ago
#2
The centripetal force is the resultant force equal to mv^2/r. The force exerted on the car by the bridge is the reaction force which must be less than the weight of the car so that the resultant force can act downwards. This means that mv^2/r = mg - R where R is the reaction force so rearranging that you get R = mg - mv^2/r. I hope that made sense.
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#3
(Original post by _zoe)
The centripetal force is the resultant force equal to mv^2/r. The force exerted on the car by the bridge is the reaction force which must be less than the weight of the car so that the resultant force can act downwards. This means that mv^2/r = mg - R where R is the reaction force so rearranging that you get R = mg - mv^2/r. I hope that made sense.
Yeah that makes sense thank you
Suppose this road was a full circle and the car could travel to the side and upside down too (like a roller coaster) what would the force of the road on the car be then when it's on the right or left side of the circle?
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1 month ago
#4
I'm not sure how it would work in that situation as neither the reaction force or weight would be acting towards the centre of the circle. Possibly a component of friction? However a similar(ish) example would be clothes in a washing machine. When they're on the sides the force on the clothes (the reaction force) would be equal to the centripetal force mv^2/r.
(Original post by Presto)
Yeah that makes sense thank you
Suppose this road was a full circle and the car could travel to the side and upside down too (like a roller coaster) what would the force of the road on the car be then when it's on the right or left side of the circle?
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#5
Ok thank you sm!
If it isn't too much trouble can you please tell me what the forces act sideways when we have a roller coaster in an outward loop?
(Original post by _zoe)
I'm not sure how it would work in that situation as neither the reaction force or weight would be acting towards the centre of the circle. Possibly a component of friction? However a similar(ish) example would be clothes in a washing machine. When they're on the sides the force on the clothes (the reaction force) would be equal to the centripetal force mv^2/r.
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1 month ago
#6
(Original post by Presto)
Ok thank you sm!
If it isn't too much trouble can you please tell me what the forces act sideways when we have a roller coaster in an outward loop?
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#7
(Original post by Eimmanuel)
Can't read all of it but thanks anyway!
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1 month ago
#8
(Original post by Presto)
Why is D??
Why not B?

Put in the equals: F = ma = mg = mv^2/r , hence a = g = v^2/r.
mg and mv^2/r are not separate entities your just describing/resolving the effect of gravitational force which is causing centripetal motion.
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#9
Yes
Thank you
Do you have any idea what would be the NRF for a roller coster when it's sideways on a loop?
(Original post by mnot)
Put in the equals: F = ma = mg = mv^2/r , hence a = g = v^2/r.
mg and mv^2/r are not separate entities your just describing/resolving the effect of gravitational force which is causing centripetal motion.
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1 month ago
#10
(Original post by Presto)
Yes
Thank you
Do you have any idea what would be the NRF for a roller coster when it's sideways on a loop?
I don't even know what NRF means: normal resistance force? i have no information about the question at hand here
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#11
Yes normal reaction force
(Original post by mnot)
I don't even know what NRF means: normal resistance force? i have no information about the question at hand here
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1 month ago
#12
(Original post by Presto)
Yes normal reaction force
well it would be quite hard to say just off the info you've provided.

But draw a free body diagram, the Normal force acts perpendicular to the interacting surface and always opposes the velocity vector and is normally just the opposing magnitude force multiplied by mu (the static friction coefficient). But if you draw the FBD correctly then annotate the resolving forces it should be more apparent.
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1 month ago
#13
I don't know about that situation sorry. I don't think you'll need to know about that for A level (I'm assuming) physics though.
(Original post by Presto)
Ok thank you sm!
If it isn't too much trouble can you please tell me what the forces act sideways when we have a roller coaster in an outward loop?
0
#14
(Original post by mnot)
well it would be quite hard to say just off the info you've provided.

But draw a free body diagram, the Normal force acts perpendicular to the interacting surface and always opposes the velocity vector and is normally just the opposing magnitude force multiplied by mu (the static friction coefficient). But if you draw the FBD correctly then annotate the resolving forces it should be more apparent.
mg acts down
mv^2/r inside towards the centre
normal opposite to Fc
Am I missing something?
How to construct the equation?
(Original post by _zoe)
I don't know about that situation sorry. I don't think you'll need to know about that for A level (I'm assuming) physics though.
I hope you're right. I have an exam tomorrow
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1 month ago
#15
Centripetal formula gives resultant force -always acts to centre of circle
you know then mv^2/r= force towards centre minus force out (as it is resultant force towards centre)
so mv^2/r =mg-R
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#16
Yes I got it thank you
(Original post by Samhunt6)
Centripetal formula gives resultant force -always acts to centre of circle
you know then mv^2/r= force towards centre minus force out (as it is resultant force towards centre)
so mv^2/r =mg-R
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