Why is normal force always perpendicular to the surface? I understand that normal force is the upward reaction force by a surface due to an external action force pushing the surface. Then, if I apply an extermal force on a non inclined surface at an angle, let's say 30 degrees, shouldnt the normal force have the exactly opposite direction and point 30 degrees above the ground, instead of 90 degrees? Does this imply that any force acting on a surface must be perpendicular to the surface? Then if i apply a force at an angle on the ground, and the force acting on the ground is only the y component,then where does the x component go? This question is really frustrating.