Direction of reaction force in a circular motion

In summary, the conversation is discussing the direction of the reaction force in a situation where a wheel is being rotated in the anticlockwise direction. There is confusion about whether the reaction force should be directed to the left or to the right, and whether the red line or the blue N3 is the resultant force. It is clarified that the resultant force is the vector sum of all the forces acting on the body, and in this case, it is the blue N3 and W combined. The red line represents the resultant force and is not necessarily related to the hypotenuse of a triangle. The centripetal force is not shown in the diagram, but it is provided by the blue N3 and W combined.
  • #1
goldfish9776
310
1

Homework Statement


Thewheel is rotated in the anticlockwise direction...The correct reaction force is drawn using the blue pen . I don't understand why the reaction force isn't directed to the left ? which is drawn using the red colour ?
IMO, the red colour should be correct because the supporting surface is on the right , ( the person sticked to the right)

Homework Equations

The Attempt at a Solution

 

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  • #2
You are probably thinking of the resultant force which should be
to the left as indicated in red. The reaction force is from the floor which
is the friction and normal force combined which would point
upwards at an angle as indicated by the blue N3. The red force
is the blue N3 and W combined - the resultant of the forces.
 
  • #3
andrevdh said:
You are probably thinking of the resultant force which should be
to the left as indicated in red. The reaction force is from the floor which
is the friction and normal force combined which would point
upwards at an angle as indicated by the blue N3. The red force
is the blue N3 and W combined - the resultant of the forces.
So, which is correct ?
Centripetal force is the resultant force of R3 and W (mg ) ?
Or R3 is the resultant force of centripetal acceleration and W(mg ) ??

P/s : I know the red line should be centripetal acceleration force now .
 
  • #4
According to N2

a = Fresultant/m
 
  • #5
andrevdh said:
According to N2

a = Fresultant/m
what is the relationship of it and the question??
 
  • #6
andrevdh said:
You are probably thinking of the resultant force which should be
to the left as indicated in red. The reaction force is from the floor which
is the friction and normal force combined which would point
upwards at an angle as indicated by the blue N3. The red force
is the blue N3 and W combined - the resultant of the forces.
Can you explain this statement in more simple sentence??
 
  • #7
andrevdh said:
You are probably thinking of the resultant force which should be
to the left as indicated in red. The reaction force is from the floor which
is the friction and normal force combined which would point
upwards at an angle as indicated by the blue N3. The red force
is the blue N3 and W combined - the resultant of the forces.
which is the resultant force ?
the red line or the blue N3?
 
  • #8
The clue for me was "reaction force".
That is the person is pushing "down" on the floor due to being spun around.
The floor reacts (reaction force), your R3, by pushing back.
We can think of this reaction force as two forces combined, the normal force,
perpendicular to the surface, and friction, parallel to the surface.
 
  • #9
According to Newton's 2nd law a body accelerates in the direction of the resultant force
as I tried to show in one of my previous posts.
According to this what should the resultant force then be? Red or blue?
 
  • #10
I can understand post # 8.
the resultant force should be the red line. but according to phytagoras's theorem , the R3 looks like resultant force , since W and Fc is perpendicular to each other ( as shown in the triangle drawn) which is making me confused now.
 
  • #11
It is just a question which forces the object is experiencing,
in this case W and blue N3. The resultant is the (vector)
sum of these. That means we can replace W and blue N3
with the red N3 in the diagram.
 
  • #12
andrevdh said:
It is just a question which forces the object is experiencing,
in this case W and blue N3. The resultant is the (vector)
sum of these. That means we can replace W and blue N3
with the red N3 in the diagram.
so , it has completely nothing to do with the hypotenuse of triangle (maths concept ) ?
The resultant force can be in any direction depending on the question although it does not comply with hypotenuse of triangle (maths concept )??
 
  • #13
The resultant force is the vector sum of all the forces acting on the body. The vector sum of two forces only equals the hypotenuse of a triangle if the two forces are at right angles (orthogonal).

Your diagram does not appear to show _all_ the forces acting on the body. I understand W = Weight. Where is the centripetal force shown?
 
  • #14
As I understand it the person is standing in cage or on a platform that is swung around.
The blue N3 and W combined provides the centripetal force.
 

Related to Direction of reaction force in a circular motion

1. What is the direction of the reaction force in circular motion?

The reaction force in circular motion is perpendicular to the velocity of the object at any given point on the circular path. This means that it is directed towards the center of the circle.

2. How does the direction of the reaction force change in circular motion?

The direction of the reaction force changes continuously as the object moves along the circular path. It is always perpendicular to the object's velocity and directed towards the center of the circle.

3. Why is the direction of the reaction force important in circular motion?

The direction of the reaction force is important because it is what allows the object to continue moving in a circular path. Without this force, the object would move in a straight line tangent to the circle.

4. Does the direction of the reaction force affect the speed of the object in circular motion?

No, the direction of the reaction force does not directly affect the speed of the object in circular motion. However, it does play a role in determining the object's acceleration, which can affect its speed.

5. How is the direction of the reaction force related to centripetal force?

The direction of the reaction force is the same as the direction of the centripetal force, which is the force that keeps the object moving in a circular path. The reaction force is simply another term for the centripetal force.

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