When normal force isn't "normal"l 1. The problem statement, all variables and given/known data A box with a certain mass is pulled across a horizontal surface by a rope at an angle. Figure out the components, the friction, the acceleration of the box, when the tension in the rope, its angle, the mass of the box, and mu are given. 2. Relevant equations F=ma, sin (theta) hypotenuse, etc... 3. The attempt at a solution I understand the solution but I'm having trouble explaining how the normal force is found. I am used to calculating the using m(g) to calculate the force of gravity. It seems as though the normal force should just be the same as gravity plus the upward component of the rope. I get that equilibrium plays a role but am just having difficulty explaining it.