1. The problem statement, all variables and given/known data
There are two important conditions for a rigid body to be in equilibrium. The first condition is that the net force on a body must be zero. The second condition is that the net torque on a body must also be zero.
2,3. Relevant equations; attempt at solution.
I apologize for the simple question but I am selfstudying physics and having a hard time with this concept.
So my question is: how are these two conditions not redundant? My initial reaction is that net torque must be zero if net force is zero, since [tex]\tau[/tex]=Fr. Then I drew this situation (a door revolving around a central pivot point) that seems to show net torque without net force (the 2 forces add up to zero but there is still rotation). The img is attached to this post.
The problem is, I still think net torque would be zero.
[tex]\tau[/tex]=Fr
[tex]\tau[/tex]=Fr
[tex]\Sigma\[/tex][tex]\tau[/tex]=(Fr)+(Fr)=0
Where am I going wrong here? Is one radius r maybe?
Thanks in advance!
