When a person pushes a crate at constant velocity, it indicates that the forces acting on the crate are balanced. This means that the force exerted by the person to the right is equal in magnitude and opposite in direction to the frictional force acting to the left.
In a free body diagram, you would typically represent the forces as arrows where the length of each arrow signifies the magnitude of the corresponding force. In this scenario, the arrow pointing to the right represents the applied force from the person, while the arrow pointing to the left represents the frictional force opposing the motion. Since the crate is moving at a constant velocity, these two arrows must be of equal length.
Additionally, there will be vertical forces acting on the crate: the weight of the crate (which acts downward) and the normal force (which acts upward). These two forces must also be balanced, meaning that the normal force equals the weight of the crate. Overall, when the net force acting on the crate is zero, it results in a state of constant velocity.