What is the normal force in A and B?

In summary, a welded square frame with four equal rods, each with mass m and length 2l, can move in the vertical plane using two frictionless small wheels at points A and B. The frame is initially at rest with its sides in a horizontal and vertical position. The problem is to determine the normal forces in points A and B at the beginning moment. Despite following the correct steps, the solution given results in an incorrect answer of 3/10*mg, whereas the correct answer should be 6/5*mg for the reaction force at point B.
  • #1
Karl Karlsson
104
12
TL;DR Summary
A welded square frame consisting of four equal rods each with mass m and length 2l can move in the vertical plane by means of two small wheels in A and B that move without friction along a horizontal and vertical track, respectively. The disc is released from rest in a position where the sides of the frame are horizontal and vertical respectively. Determine the normal forces in A and B at the beginning moment.
Skärmavbild 2019-09-27 kl. 12.20.59.png

A welded square frame consisting of four equal rods each with mass m and length 2l can move in the vertical plane by means of two small wheels in A and B that move without friction along a horizontal and vertical track, respectively. The disc is released from rest in a position where the sides of the frame are horizontal and vertical respectively. Determine the normal forces in A and B at the beginning moment.
 
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  • #2
I have written on swedish but i think it will be quite easy to understand. As you can see if you watch my solution i get the wrong answer even though i feel like i am doing everything correct. The reaction force in B should be 6/5*mg, where as my answer is 3/10*mg. My attempt:
9a2171cd-4af8-4046-9238-aad500abfbf5_img-0389.jpg
 
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  • #3
1569681856122.png

For some reason i can't have more than one picture per post
 

Related to What is the normal force in A and B?

1. What is the definition of normal force?

The normal force is the force that a surface exerts on an object that is in contact with it. It is always perpendicular to the surface and acts in the opposite direction of the force that is pressing the object against the surface.

2. How is the normal force calculated?

The normal force is calculated by multiplying the object's mass by the acceleration due to gravity, which is typically 9.8 m/s². This calculation takes into account the force of gravity acting on the object and the surface's resistance to that force.

3. What is the difference between normal force in A and B?

The normal force in A and B refers to the normal force acting on an object at two different points on a surface. The magnitude of the normal force may be different at these two points depending on the angle of the surface and the weight of the object. However, the direction of the normal force will always be perpendicular to the surface at both points.

4. Can the normal force be negative?

No, the normal force cannot be negative. It is always a positive value, as it represents the force that is preventing an object from falling through a surface. If the normal force were to become negative, it would mean that the object is no longer in contact with the surface.

5. How does the normal force affect an object's motion?

The normal force does not directly affect an object's motion. It is a balancing force that counteracts the force of gravity and prevents the object from sinking into a surface. However, it can indirectly affect an object's motion by changing the normal force can change the object's frictional force, which can then affect its motion.

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