Under what conditions does an object continue moving at a constant speed?

An object continues moving at a constant speed when there is no net force acting on it, in accordance with Newton's First Law of Motion. This law states that an object at rest will remain at rest, and an object in motion will continue in motion with the same speed and in the same direction unless acted upon by a net external force.

When there is no net force, the forces acting on the object are balanced, meaning that any forces in one direction are countered by equal forces in the opposite direction. This balance allows the object to maintain its velocity, leading to constant speed and, if applicable, constant direction. This situation is often referred to as being in a state of constant motion or equilibrium.

In contrast, if a net force is acting on an object, it will either accelerate or decelerate, changing its speed. The presence of friction is also a force that typically opposes motion, which means it would not help maintain constant speed without a compensating force. The condition of being in a vacuum pertains to the absence of air resistance but does not inherently ensure constant speed without the condition of no net force.