6. A box of tools rests in the back of a pickup truck. The truck accelerates to the north and the box remains at rest in the truck. The direction of the friction force on the box of tools is _____. north south zero None of the Above

When the force accelerates in the northern direction, a box that is untied to the truck, tends to remain at a spot. if this happens, the truck will move from under the box, which will fall down after the truck moves. Considering the fact that the box does not fall off the truck in motion, there is therefore a frictional force that acts to cause the acceleration of the box as the truck accelerates, to keep the box resting on the truck. This frictional force acts in the same direction as the truck, but has a lesser magnitude than the acceleration of the truck, because if the truck moves too fast beyond a certain acceleration, it will leave the box behind, which is seen as the box sliding off the truck.

I attached a diagram to help you understand the forces acting on the box better.