If there is no friction acting on an object, and no other external forces are present, the object will indeed move at a constant velocity. This is known as uniform or constant velocity motion.
In the absence of external forces, Newton's first law of motion states that an object at rest will stay at rest, and an object in motion will continue moving in a straight line at a constant velocity. In this case, the absence of friction means there are no forces opposing the object's motion, allowing it to maintain a steady velocity.
However, it's important to note that although the object is moving at a constant velocity, it doesn't necessarily mean its kinetic energy will remain constant. Kinetic energy (KE) is defined as the energy possessed by an object due to its motion and is given by the equation:
KE = (1/2) * m * v^2
where m is the mass of the object and v is its velocity. While the velocity remains constant in the absence of external forces, the kinetic energy can still change if the mass of the object changes.
For example, if the object loses mass (e.g., due to a fragment breaking off), its kinetic energy will decrease since kinetic energy is directly proportional to the mass. Conversely, if the object gains mass, its kinetic energy will increase. Therefore, even in the absence of friction, changes in the object's mass can result in changes to its kinetic energy.