# Normal force of a body over a circular bridge

• B

## Summary:

Hi! Can somebody please explain me the concept of normal force over convex and concave bridge?

## Main Question or Discussion Point

I am not able to understand why normal force on top in a vertical circular motion the least.
Why do we get these equations:
N=mg-mv2/r (convex bridge)
N=mg+mv2/r (concave bridge)

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PhanthomJay
Homework Helper
Gold Member
Are you familiar with centripetal acceleration, free body diagrams, and Newton's 2nd law? At the top of the circle (convex curve), draw a free body diagram of the forces acting on the body, with the body in contact with the surface on the outside of the circle. Do the same at the bottom of the circle (concave curve), with the body in contact with the surface on the inside of the circle. In each case, what is the direction of the two forces that act on the body?

• Shashwat02, berkeman and tnich
The normal force acts upwards and force due to gravity and centripetal force act downward in convex bridge.
In concave bridge normal force acts upwards along with centripetal force and force due to gravity acts downwards.
Please explain me why normal force at topmost point in vertical circular motion is least and highest at bottom.

A.T.
Please explain me why normal force at topmost point in vertical circular motion is least and highest at bottom.
How are the three forces you named related quantitatively? Have you looked at Newton's 2nd Law?

How are the three forces you named related quantitatively? Have you looked at Newton's 2nd Law?
Consider FBD of a vehicle on the top of a convex and concave bridge.

Are you familiar with centripetal acceleration, free body diagrams, and Newton's 2nd law? At the top of the circle (convex curve), draw a free body diagram of the forces acting on the body, with the body in contact with the surface on the outside of the circle. Do the same at the bottom of the circle (concave curve), with the body in contact with the surface on the inside of the circle. In each case, what is the direction of the two forces that act on the body?
The normal force acts upwards and force due to gravity and centripetal force act downward in convex bridge.
In concave bridge normal force acts upwards along with centripetal force and force due to gravity acts downwards.
Please explain me why normal force at topmost point in vertical circular motion is least and highest at bottom

jbriggs444
Homework Helper
2019 Award
The normal force acts upwards and force due to gravity and centripetal force act downward in convex bridge.
In concave bridge normal force acts upwards along with centripetal force and force due to gravity acts downwards.
Please explain me why normal force at topmost point in vertical circular motion is least and highest at bottom
Please realize that "centripetal" and "centrifugal" are not types of forces. They are directions in which a force can act: toward the center or away from the center.

On a surface that is concave, the normal force from the surface against an object is a centripetal force. On a convex surface, the normal force from the surface against an object is a centrifugal force.

[Confusingly, the term "centrifugal" is often applied to a very specific force -- the apparent outward inertial force associated with the adoption of a rotating frame of reference]

PhanthomJay