What is Linear motion: definition, types with more examples?

Linear motion is a basic concept of all motion. If an object moves in a straight line it is called linear motion. It is often referred to as rectilinear motion and has one spatial dimension. However, when one object moves from one location to another location, it is said to be the motion of the object.

Linear motion: definition

Linear motion is a basic concept of all motion. If an object moves in a straight line it is called linear motion. It is often referred to as rectilinear motion and has one spatial dimension. Whenever one object moves from one location to another location, it is said to be the motion of the object.

Newton’s first law of motion says an object will either be at rest or continue to move in a straight line with constant velocity unless it is affected by any external force depending on its initial condition of motion. Newton’s first law of motion is also called as law of inertia.

In our daily life, we always encounter motion and external forces. The forces like gravity and friction can make an object to change the direction of its motion even if no force is applied by any, body or object. In such a case, we may not say the motion of the object is linear. One may confuse linear motion with general motion. However, in the case of general motion, an object has both magnitude and direction where the object’s position and velocity are described by a vector. The velocity of the object is defined as the rate of change of displacement.

In classical Newtonian mechanics, there is no distinction between the rest and uniform motion of an object in a straight line. They may be considered as in the same state of motion seen by two different observers, one moving at the same velocity as the object, and the other moving at constant velocity with respect to the object.

Types of linear motion

Linear motion can be classified into two types, such as uniform and Non-uniform linear motion.

Uniform linear motion;

If an object moves with a constant velocity and in the same direction in a straight line is known as uniform linear motion. During such motion, the direction as well as the magnitude of the velocity remain constant. We may take some examples in this regard.

• A car is running at 50 km/hr on a straight road: A car is moving at the constant speed of 50km/hr throughout its journey without making any deviation means acceleration is zero.
• A bike is running at 40km/hr on a straight road: Like the above-referred case, a two-wheeler is running at 40km/hr with zero acceleration.
• A mango is falling: When a mango falls, it maintains the same velocity with zero acceleration.

Acceleration is defined as the change in velocity in one second. It is a vector quantity. Its units in the CSG system cms^-2and MKS system ms^-2.

Non-uniform linear motion;

When an object moves with a variable velocity and in one direction in a straight line is known as non-uniform linear motion. During such motion direction remains constant, however, the magnitude of the velocity changes. Examples;

• Movement of an aircraft during landing: At the time of landing the pilot controls the speed of the aircraft according to the situation. In the process, the pilot changes acceleration.
• Running of athletes in a marathon: In a marathon, different athletes run at different speeds on a specific track.
• A horse running: We may not expect a horse to run at uniform speed throughout the race.

Equations of the non-uniform linear motion are often written as;

vt=v₀+a t

d=v₀t+1/2a t²

vt²=v₀²+2a d

Where v₀ is the initial speed in meters/second, vt is the final speed in meters/second, a is acceleration in meters/second², t is the time interval in seconds, and d is the distance covered in meters.

Some more examples of linear motion

• Firing a bullet.
• Elevators or lifts.
• Free fall of an object.
• Swimming in a water lane in the competition.
• The motion of a bike on a straight road.
• sliding by the child.
• Cutting a block of wood by saw.
• Walking on a straight road.
• bowling in cricket.

Bottom line

Whenever an object moves from one location to another location, it is said to be the motion of the object. However, when an object moves in a straight line referred to as linear motion it can be uniform or non-uniform. During our daily life, we often encounter motions in one or more forms.