Forces acting on wedge and block?

A force is acting horizontally on a wedge, as the picture shows:





http://img215.imageshack.us/my.php?image...





The wedge has mass M and the block has mass m. Therefore:





a) the normal force that the floor applies on the wedge depends on the force F?





b) What is the force needed to maintain the block static?





c) What happens if force F is too big?





For a) I have that the normal is independent of the force F. For b) I have that F=g tan ά(M+m), and for c) I think that the blocks goes up. Is that correct?

Forces acting on wedge and block?
a) the normal force that the floor applies on the wedge depends on the force F?


It really depends. For example, (1) the normal force depends on the force F when i) the block is also accelerate (either up or down) on the wedge, and ii) the wedge is moving in air with air friction, and (2) the normal force does not depend on the force F when air friction is ignored as well as there is no relative motion between the wedge and the block.





b) What is the force needed to maintain the block static?


Make assumptions as stated in (2) above. Also it seems to me that there is no friction between the wedge and the block. There are 3 forces in equilibrium on the block: mg, normal force by wedge, and acceleration force. The normal force must be mg/cos α, and therefore the acceleration force must be mg*tan α. Hence the common acceleration of the wedge and the block is g*tan α, or the force F = (M+m)g*tan α.





You are perfect on both (b) and (c).

gift