# Direction of normal reaction of the Ferriw wheel at the high

• goldfish9776
In summary, the conversation discusses the direction of the normal reaction force in a roller coaster ride. It is explained that in circular motion, there must be an inward force and the reaction force to this is the outward force acting on the person. Therefore, when the person is inverted in the ride, the normal reaction force is acted downwards towards the center of the circle.
goldfish9776

## Homework Statement

As you can see , the writer state that the direction of normal reaction force(R) is acted upwards , I have another book state that the normal reaction force (R) is acted downwards , which one is correct ?

## The Attempt at a Solution

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#### Attachments

• IMG_20150627_072125[1].jpg
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If the other source is describing the normal force of the seat on the passenger then it is incorrect unless the person is inverted (so that their head is toward the center). The reaction force is drawn correctly in the image you posted.

goldfish9776 said:

## Homework Statement

As you can see , the writer state that the direction of normal reaction force(R) is acted upwards , I have another book state that the normal reaction force (R) is acted downwards , which one is correct ?
The image you attached says nothing about a "normal reaction force". It speaks of the reaction force of the basket on the person without specifying what surface it might be perpendicular to.

The term "normal reaction force" taken at face value would mean a force which is:

1. "normal" -- that is, perpendicular to some surface. If working in two dimensions, "normal" means perpendicular to a line.
2. A reaction force -- that is, the third law partner of some other force.

The force of the person on the basket would be downward and would be a "normal reaction force" because it is perpendicular to the seat and is a reaction force to the force of the seat on the person.

brainpushups said:
If the other source is describing the normal force of the seat on the passenger then it is incorrect unless the person is inverted (so that their head is toward the center). The reaction force is drawn correctly in the image you posted.
ok , thanks for your reply . So can you explain why the direction of the normal reaction force is acted downwards when the person is inverted at the highest position ?

goldfish9776 said:
ok , thanks for your reply . So can you explain why the direction of the normal reaction force is acted downwards when the person is inverted at the highest position ?

This would be a different ride (think of a roller coaster going through a loop). A centripetal force is required to keep the passenger in circular motion. This would be the force provided by the seat and since the seat is pointing inward the force is inward.

Of course, the ride must be moving fast enough. Suppose the ride got stuck at the top. Then the reaction force of the harness would need to prevent the person from falling in (down) and would therefore be up.

**edited for clarity**

brainpushups said:
This would be a different ride (think of a roller coaster going through a loop). A centripetal force is required to keep the passenger in circular motion. This would be the force provided by the seat and since the seat is pointing inward the force is inward.

Of course, the ride must be moving fast enough. Suppose the ride got stuck at the top. Then the reaction force of the harness would need to prevent the person from falling in (down) and would therefore be up.
sorry , i still don't understand why the rection frce is acted downwards in the roller coaster ride...Mind to explain further?

brainpushups said:
This would be a different ride (think of a roller coaster going through a loop). A centripetal force is required to keep the passenger in circular motion. This would be the force provided by the seat and since the seat is pointing inward the force is inward.

Of course, the ride must be moving fast enough. Suppose the ride got stuck at the top. Then the reaction force of the harness would need to prevent the person from falling in (down) and would therefore be up.

**edited for clarity**
can I explain in this way ? If the person is inverted (in roller coaster ride) the person is actually 'sticked' to the seat , there's a force to cause it to do so . So , the reaction force should be opposite to the force , to support it from falling... So , the normal reaction force is acted downwards ( towards the centre of the wheel) * correct me if I'm wrong*

If you swing something around in a vertical circle that is attached to a rope you need to pull inward. This is pull is the centripetal force that allows for the circular motion. Cut the string when the object is at the top and it will fly off horizontally; falling due to gravity.

Any type of circular motion requires an inward force. In the case of the looping roller coaster (where the passenger's head is inward to the circle) this force is provided by the seat. The seat is above the person and there is nothing else to push inward...

goldfish9776 said:
can I explain in this way ? If the person is inverted (in roller coaster ride) the person is actually 'sticked' to the seat , there's a force to cause it to do so

There's no force which causes the person to be stuck to the seat (a common misconception). Rather, the motion of the person would be in a straight line if it weren't for the seat providing the inward force.

How does this sit with you - because the motion is circular there must be an inwardly directed force. The reaction force to the inward force of the seat on the person is the outward force of the person on the seat.

brainpushups said:
The seat is above the person and there is nothing else to push inward...
So, the normal reaction force is acted towards the circle ( downnwards) to support the person.??

brainpushups said:
This is pull is the centripetal force that allows for the circular motion.

.
So , the centripetal force = R (reaction force + mg ) in this case . this motion is just like roller coaster case , right ? I know what do you mean , but now , i am asking about
brainpushups said:
There's no force which causes the person to be stuck to the seat (a common misconception). Rather, the motion of the person would be in a straight line if it weren't for the seat providing the inward force.

How does this sit with you - because the motion is circular there must be an inwardly directed force. The reaction force to the inward force of the seat on the person is the outward force of the person on the seat.

do u say it wrongly ? IMO, in the roller coaster ride , the force of the person of the seat in is upward direction , since the seat is at the top . So , the reaction force is acted downwards ? Correct me if I'm wrong.

goldfish9776 said:
So, the normal reaction force is acted towards the circle ( downnwards) to support the person.??

In the case of the loop the loop the normal force of the seat on the person is toward the center of the circle... Whether or not it is the 'action' or reaction' is arbitrary.

QUOTE="goldfish9776, post: 5152596, member: 561115"]do u say it wrongly ? IMO, in the roller coaster ride , the force of the person of the seat in is upward direction , since the seat is at the top . So , the reaction force is acted downwards ? Correct me if I'm wrong.[/QUOTE]

Don't get hung up on this whole action/reaction distinction. I was saying that if you consider the inward force of the seat to be a necessary requirement for circular motion (action) then the reaction to this is the outward force of the person on the seat. Flip the action/reaction labels around if you wish.

goldfish9776
The normal force is perpendicular to the supporting surface.
I came across this statement when I googled out some informations . In the roller coaster case , can I say that the normal recation force is acted downwards because of it is perpendicular to the supporting surface . If I consider the normal reaction force is in upward position , then the normal reaction force is in 180 degree form the supporting surface , which is contrary top the above statement ...Correct me if i 'm correct

goldfish9776 said:
The normal force is perpendicular to the supporting surface.
I came across this statement when I googled out some informations . In the roller coaster case , can I say that the normal recation force is acted downwards because of it is perpendicular to the supporting surface . If I consider the normal reaction force is in upward position , then the normal reaction force is in 180 degree form the supporting surface , which is contrary top the above statement ...Correct me if i 'm correct
In the diagram you posted, the supporting surface is a horizontal seat. The reaction force is vertical. Last time I checked, horizontal and vertical were perpendicular to each other, not at 180 degrees.
You don't describe the situation being discussed in the 'other' book. Without that, we have no way to resolve your confusion. Brainpushups is guessing that the other book considers a rollercoaster, not a Ferris wheel, and has the passenger inverted.
brainpushups said:
In the case of the looping roller coaster (where the passenger's head is inward to the circle) this force is provided by the seat. The seat is above the person and there is nothing else to push inward...
Umm... Gravity?

haruspex said:
In the diagram you posted, the supporting surface is a horizontal seat. The reaction force is vertical. Last time I checked, horizontal and vertical were perpendicular to each other, not at 180 degrees.
You don't describe the situation being discussed in the 'other' book. Without that, we have no way to resolve your confusion. Brainpushups is guessing that the other book considers a rollercoaster, not a Ferris wheel, and has the passenger inverted.

Umm... Gravity?
Ya, I noticed that the person is inverted in the other book, the normal reaction is acted in downward position

haruspex said:
Umm... Gravity?

Indeed, that was not well phrased. The centripetal force at the top is the sum of the gravitational force and the force of the seat.

## 1. What is the direction of the normal reaction force on a Ferris wheel at the top?

The normal reaction force on a Ferris wheel at the top is directed downwards, towards the center of the wheel. This is due to the force of gravity pulling the riders towards the center of the wheel.

## 2. How does the direction of the normal reaction force change as the Ferris wheel rotates?

The direction of the normal reaction force changes constantly as the Ferris wheel rotates. At the bottom of the wheel, the normal reaction force is directed upwards, away from the center of the wheel. As the wheel rotates, the direction of the normal reaction force gradually shifts from upwards to downwards at the top of the wheel.

## 3. What is the significance of the direction of the normal reaction force on a Ferris wheel?

The direction of the normal reaction force on a Ferris wheel is significant because it helps to keep the riders safely in their seats. As the wheel rotates, the normal reaction force acts as a balancing force to counteract the force of gravity and prevent the riders from falling out of their seats.

## 4. How does the direction of the normal reaction force affect the speed of the Ferris wheel?

The direction of the normal reaction force does not directly affect the speed of the Ferris wheel. However, it plays a role in maintaining the balance and stability of the wheel, which can indirectly impact the speed of the wheel. If the normal reaction force is too weak or too strong, it could cause the wheel to speed up or slow down, respectively.

## 5. Can the direction of the normal reaction force change during a ride on a Ferris wheel?

Yes, the direction of the normal reaction force can change during a ride on a Ferris wheel. As the wheel rotates and the riders move up and down, the direction of the normal reaction force will also shift accordingly. Additionally, external factors such as wind or uneven loading of the wheel can also cause changes in the direction of the normal reaction force.

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