# What is the Direction of Normal Force in Static Equilibrium on a Ramp?

• Coderhk
In summary, the conversation discusses the normal force on a ramp and its components. The question is whether the normal force is perpendicular to the ramp, and the answer is yes, with a vertical component of N cos(α). There is also a discussion about the free body diagram and the correct angles to use.
Coderhk

## Homework Statement

Part a of the image below. When I try to solve this question, I can't get the solution in the answer key. In the answer key the y component of the normal force is NCos(alpha) in the last line. Does the normal force not point perpendicular to the ramp?

## Homework Equations

F=ma=0 since we are in static equilibrium
sum of torques = 0;

## The Attempt at a Solution

In the picture below.

#### Attachments

• IMG_20181129_204423.jpg
22.6 KB · Views: 250
Coderhk said:
Does the normal force not point perpendicular to the ramp?
It does indeed, but doesn't that mean that the vertical component is N cos(α) as stated?
In the attachment I see Ny evaluated as N sin(β-α). That would be taking N as acting along the bar, not normal to the ramp.

haruspex said:
It does indeed, but doesn't that mean that the vertical component is N cos(α) as stated?
Shouldn't it be Nsin(beta-alpha)? I got to that answer based on my right most diagram. If the normal force was to be perpendicular to the surface it would be parallel to the bar right?

Coderhk said:
. If the normal force was to be perpendicular to the surface it would be parallel to the bar right?
No, that would only be true if the bar were normal to the surface, which it is not.

haruspex said:
No, that would only be true if the bar were normal to the surface, which it is not.
should the free body diagram look like this instead?

#### Attachments

• temp.jpg
19.5 KB · Views: 233
Coderhk said:
should the free body diagram look like this instead?
It looks roughly right, but there seems to be (faintly) an angle labelled α between the normal and the horizontal. That would not be right.
The angle between the surface and the horizontal is α.

Last edited:

## 1. What is the direction of the normal force?

The direction of the normal force is perpendicular to the surface of contact between two objects. It always acts in a direction that is away from the surface, pushing the objects apart.

## 2. How is the direction of the normal force determined?

The direction of the normal force is determined by the surface of contact between two objects. It is always perpendicular to this surface, regardless of the orientation or angle of the objects.

## 3. Does the direction of the normal force change?

The direction of the normal force can change if the orientation or angle of the objects in contact changes. However, it will always remain perpendicular to the surface of contact.

## 4. What is the significance of the direction of the normal force?

The direction of the normal force is important in determining the stability and equilibrium of objects in contact. It also plays a role in calculating frictional forces and determining the motion of objects on inclined surfaces.

## 5. Can the direction of the normal force be negative?

The direction of the normal force is always perpendicular to the surface of contact and cannot be negative. However, the magnitude of the normal force can be negative if the objects in contact are pulling away from each other instead of pushing.

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