What is the normal force in A and B?

Sep 2019
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 frictionally along a horizontal or 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.

My attempt:

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.
Last edited:
Jun 2016
I guess that the only source of force is gravity, which is moving in the ey direction.

At any time after the start time,
there will be lateral forces caused by the geometry.

But at the beginning time the only forces will be in the ey direction,