A crate is being pushed at a constant speed across the floor. The gravitational force on the crate is 80N, and the applied force is 50N. What are the other force(s) acting on the crate?

Friction force.

Explanation:

Force is defined as a pull or push acting on an object that changes the speed or direction of the motion.

When a crate is is being pushed at a constant speed across the floor along with gravitational force and the applied force, there will be a force of friction applied by the floor on the opposite direction of applied force.

Friction always opposes the applied force and resist the changes in the motion of the object.

Hence, the correct option is Friction force.