1. The problem statement, all variables and given/known data This question comes from a lab that we did a while ago: Hang a painting on a nail by a thread. The weight of the painting was 0.4 kg. a) Calculate the force in the nail that holds up the painting. b) Calculate the forces that work on the thread holding the painting in place. 2. Relevant equations Newton's second law, F=mg And the normal force that is as large but working in the opposite direction, since the painting is in equilibrium. 3. The attempt at a solution a) When attempting to solve this question I observed the phrasing "in the nail", does this mean that I have to weigh the nail and then calculate the gravitational force, and then the normal force from the wall that holds the nail in equilibrium? Or does this mean that I have to use the weight of the painting including the thread and then make this the force in the nail? b) Now what I did was draw the following picture http://img182.imageshack.us/img182/382/tavlan6zw8.png [Broken] I made the assumption that the gravitational force works from the centre of the painting, and that the normal force works on the painting from the thread in two points in the opposite direction (i.e., the points where the thread holds the painting).. I'm having trouble coming to terms with what forces work on which objects.. I could really use some help, thanks!