Final answer:
The force on the desk when a cat jumps off by applying a force of 50.0 N is also 50.0 N, in accordance with Newton's Third Law of Motion.
Step-by-step explanation:
The force exerted on a desk when a cat with a mass of 5.00 kg pushes on it with a force of 50.0 N is equal to the force the cat applies, due to Newton's Third Law of Motion, which states that for every action there is an equal and opposite reaction. Therefore, if the cat applies a force of 50.0 N to jump off the desk, the force on the desk is also 50.0 N in the opposite direction. This concept is demonstrated in various scenarios, such as when a person exerts a force on an object, and the friction force must be overcome for the object to move.