A crate accelerates horizontally but has no vertical acceleration. What do Newton's laws give for the net force in each direction?

1. Before writing net force equations, decide whether the system accelerates in each direction. 2. If the acceleration is zero in a direction, the net force is zero in that direction. 3. If the acceleration is not zero, the net force in that direction equals the mass times the acceleration. 4. Here the crate accelerates horizontally, so the horizontal net force is ma. 5. There is no vertical acceleration, so the vertical net force is zero. _Source: OpenStax College Physics (CC BY 4.0), Ch 4 "Dynamics: Force and Newton's Laws of Motion", section 4.6 Problem-Solving Strategies_