Issue with understanding aspects of moments

  • Thread starter Dongorgon
  • Start date
  • Tags
    Moments
In summary, the conversation is about a problem involving normal reactions at angles. The question involves finding the force in a propped loft door and the normal reaction at the hinge. The solution for the force in the strut is straightforward, but finding the normal reaction at the hinge is more challenging. The person is unsure how to approach the situation and their attempted solution gives a wrong answer. They ask for help from Dongorgon.
  • #1
Dongorgon
20
0
Hi all, currently having a few issues with understanding a few aspects of questions involving normal reactions at angles. Just an example of where I am going wrong:

'A loft door OA of weight 100N is propped open at 50 degrees to the horizontal by a strut AB. The door is hinged at O. OA=OB=1m.'

To find the force in the strut, it was fairly straightforward. Taking moments about '0';

0.5x100sin(40)=Fsin(115)

Hence F = 35.46...N

However, when trying to calculate the normal reaction at the hinge, I'm truly lost how to consider the situation?

My attempt leads to: R+(35.46...)cos(25)=100
Which gives R as 67.9 N, yet is a wrong answer?! Any help would be much appreciated, thanks,
 
Mathematics news on Phys.org
  • #2
Hi Dongorgon! :smile:

You'll need a moments equation.

Choose any point, and take moments about it (the end of the strut would be easiest). :wink:
 

Related to Issue with understanding aspects of moments

1. What are moments in physics?

Moments in physics refer to the turning effect of a force around a pivot point. It is a measure of the ability of a force to cause an object to rotate.

2. How are moments calculated?

Moments are calculated by multiplying the magnitude of a force by the perpendicular distance from the pivot point to the line of action of the force. This can be represented by the equation M = F x d, where M is the moment, F is the force, and d is the distance.

3. What is the difference between a clockwise and counterclockwise moment?

A clockwise moment refers to a moment that causes an object to rotate in a clockwise direction, while a counterclockwise moment causes the object to rotate in a counterclockwise direction. The direction of rotation is determined by the direction of the force and the direction of the perpendicular distance from the pivot point.

4. How do moments affect equilibrium?

Moments play a crucial role in determining the equilibrium of an object. In order for an object to be in equilibrium, the sum of all clockwise moments must be equal to the sum of all counterclockwise moments. This is known as the principle of moments or the law of moments.

5. What are the practical applications of understanding moments?

Understanding moments is important in various fields such as engineering, architecture, and physics. It is used to design stable structures, calculate the strength of materials, and analyze the stability of objects. It is also used in everyday activities such as opening a door, using a wrench, and balancing objects.

Similar threads

Finding the Normal Force on the Rod of a Paper Roll
    • Introductory Physics Homework Help
Replies
9
Views
3K
Frustrated by how physics is generally explained/taught
    • STEM Educators and Teaching
2
Replies
37
Views
7K
Note the comment on SR herein:
    • Special and General Relativity
Replies
2
Views
2K
Mathematica This Week's Finds in Mathematical Physics (Week 241)
    • MATLAB, Maple, Mathematica, LaTeX
Replies
8
Views
3K

Hot Threads

Recent Insights

Back
Top