When a body or item goes along a straight line or a curve in a plane, it is said to be in linear motion. Athlete sprinting in a straight line. Rectilinear motion (also a form of linear motion) is defined as a moving body/object that follows only a straight route. A car driving down a road would be an example of rectilinear motion.
Linear motion is the most common type of motion experienced by objects on Earth. An object in linear motion stays in one place but moves along a straight line (or more generally, a plane). The term "linear" comes from the fact that lines can be drawn through any point on such an object to find all other points on it later visited by the object. Thus, everything on such an object is in a line.
A typical example of linear motion is an athlete running in a straight line. The earth's surface is curved, so an object in orbit around the planet will experience non-linear motion - its path through space is not a straight line. However, even though astronauts move in a circle, they are still considered to be in linear motion because their paths lie in a plane. As long as we're distinguishing between types of motion, satellites in elliptical orbits follow arcs that lie within a plane, so they are also in rectilinear motion.
Linear motion is the motion that an item naturally exhibits while travelling in a straight path. Newton's First Law of Motion states that an item that is not influenced by any force will continue in a straight path eternally. As long as there are no forces acting on it, an item will keep moving in a straight line.
In reality, most items do not travel in a perfectly straight line; rather, they curve a little bit because their weight causes them to roll along the ground. However, assuming that the curving is slow enough to be ignored, then the item can be treated as if it were traveling in a straight line. For example, when you throw a ball up in the air, it travels in a curved path but it is still considered to be in linear motion because the only part of the trajectory that matters is the portion near the end when it is going upward (or downward) away from (or toward) the Earth.
Also, objects traveling at high speeds exhibit almost perfect linearity. If you watch a baseball flying through the air, you will see that even though it is traveling in a curved path, it stays close to the line that connects the center of its mass with the point where it was last seen.
Finally, some machines use linear motors instead of rotary motors.
Linear motion is often referred to as rectilinear motion. It is one-dimensional motion in a straight line. When an object moves in a straight path, its location changes over time. Circular motion is the movement of an item in a circular direction or across a circle. This type of motion can be two-dimensional, such as the rotation of a wheel within a frame or three-dimensional, such as the ascent and descent of a ladder.
An example of linear motion is when someone walks down the street. The person's location will not change unless they stop walking. If someone drives down the same road, their location will change since there are curves in the road. A car in circular motion would go around in a loop. Location: starting point; ending point; starting point; ending point; etc.
Linear motion is useful for objects that do not get too far from where they started. For example, if you push a button on the side of a wall and it pushes back, then you have done some linear motion. However, if you were to push the button and it took you all around the room, that would be circular motion and you would need another device to do something about getting you back to where you started.
There are many devices used for linear motion including wheels, axles, rods, belts, and screws.
Moving in a straight path is referred to as linear motion (or rectilinear motion). When all points in a body travel the same distance in the same period of time, this is referred to as translational motion. Translatory motion does not necessarily necessitate a straight line movement of the item. Rotary motion is an example of translatory motion: An object rotating about an axis will experience axial displacement.
Linear motion is useful for objects that do not exceed a certain weight, since it is easier to control than rotary motion. Also, linear motion is usually more convenient and less energy-intensive than rotary motion. Engines used for vehicles and machinery tend to be designed with this type of motion because it is easy to incorporate into their structure. Bearings, couplings, and gears are used to transmit power from one part of the machine to another while allowing free rotation.
When you push or pull on a rope, it creates linear motion because you are moving the end of the rope away from you or toward you. This makes sense if you think about it: If you want the rope to move in a straight line, you need something else to keep it there. For example, if you tie one end of the rope to a tree and then pull on the other end, the tree will stop the rope from moving in a straight line, so it's not useful for pushing objects unless you're willing to let it out farther than the object can go.