Uniform straight line motion is a type of linear motion. It works according to Newton's First law of motion i.e. , objects that do not experience any net force will continue to move in a straight line with a constant velocity until they are subjected to a net force. Hence, option 'C' is the right answer.

Motion without Force

Introduction:
Motion is the change in position of an object over time. It can occur in different forms, such as circular motion, straight line motion, elliptical motion, and projectile motion. While most types of motion require a force to maintain them, there is one type of motion that does not require force to keep it going. This type of motion is called uniform straight line motion.

Uniform Straight Line Motion:
Uniform straight line motion is the motion of an object moving in a straight line with a constant speed. In this type of motion, the object covers equal distances in equal intervals of time. It does not change its direction or speed during the motion. Examples of uniform straight line motion include a car moving on a straight road with a constant velocity or a ball rolling on a frictionless surface.

Explanation:
Uniform straight line motion does not require force to maintain it because there are no external forces acting on the object to change its state of motion. According to Newton's first law of motion, an object at rest or in uniform motion will continue to remain in that state unless acted upon by an external force.

In the case of uniform straight line motion, the object is already in motion with a constant speed, and there are no forces acting on it to change its state of motion. The absence of external forces means that there is no need for additional force to maintain the motion.

Unlike circular motion or elliptical motion, which require a centripetal force to keep the object moving in a curved path, uniform straight line motion does not involve any change in direction or acceleration. Therefore, no force is required to maintain the motion.

Conclusion:
In summary, uniform straight line motion is the only type of motion that does not require force to maintain it. This is because there are no external forces acting on the object to change its state of motion. Objects in uniform straight line motion will continue to move at a constant speed in a straight line until acted upon by an external force, in accordance with Newton's first law of motion.