# Why the force is changing when I press something, if $a=0$? [closed]

As the second Newton's law says $F=ma$. Why the force is increases, when I press something, if $a=0$?

• Fhe $F$ in $F=ma$. Is the net force. If there is no acceleration it is because some other force, opposing the motion, is increasing at the same time. – M. Enns Feb 2 '18 at 19:45
• @M.Enns, "net force"? What does it mean? I've finded a link – Артур Клочко Feb 2 '18 at 19:48
• @M.Enns, so the other force is the electromagnetism? – Артур Клочко Feb 2 '18 at 19:51
• The net force is the vector sum of all the forces acting on an object. Say you are pressing a book down onto a table, the net force would be the sum of the force you apply plus the force of gravity on the book plus the normal force of the table acting upwards on the book. – M. Enns Feb 2 '18 at 19:51

I believe you are referring to the force of static friction which is Ffriction = $\mu$*FNormal Until the applied force exceeds the value of the static friction the body remains at rest. 