**What Are the Quantities in the Concept of Linear Motion?**

Linear motion is a term in physics that refers to the movement of an object that takes place along a straight path without changing direction. In linear motion, an object moves from one point to another in a straight line, without deviating to the left or right. This concept helps to understand and analyze various movement phenomena in physics, such as measuring speed, acceleration, and distance traveled by an object while moving in a straight line.

**Definition of Linear Motion**

Motion itself is a change in the position of an object that is observed, namely from a reference point. The reference point in question is interpreted as the starting point of the object or also the point where the observer is located. This linear motion is the motion of an object whose path is a straight line. This type of motion is called a regular translation. In the same time span, there is a displacement of the same magnitude.

This linear motion becomes a translational motion, which is the movement of an object that moves without rotating. It is called a straight line because its path is a straight line. For example, the hope can be seen in a car moving forward, the movement of an apple falling from a tree, and each object that moves on a straight path.

If an object moves, the object will then experience a change in distance and can experience a change in position or what is commonly called displacement. Here is a further discussion:

This distance is the length of the entire path traveled by a moving object. The distance only has a value.

This displacement is the length of the straight path measured from the initial position to the final position of the object. This displacement has a value and direction.

**Types of Straight Motion**

**Uniform Straight Motion (GLB)**

Uniform Straight Motion is used to describe a stable speed. For example, an athlete who travels a distance of 30 meters in 6 seconds. This means that this athlete travels a distance of 5 meters every second. The ability of the athlete above is interpreted as speed with the mathematical formula v = s / t with units of m / s (meters per second) or km / h (kilometers per hour).

**Uniformly Accelerated Linear Motion (GLBB)**

Uniformly Accelerated Linear Motion is used to define the acceleration or deceleration of the movement of an object. For example, when the car first moves, it will experience acceleration, while when approaching the destination it will experience deceleration.

This shows that the speed of this car is changing. To calculate this speed, it can be formulated as a = ? v / ? t with units of m / s2 (meters per second squared). The acceleration of an object as a straight motion does not only apply to objects moving horizontally. Acceleration also occurs in objects moving vertically. Objects moving vertically can experience acceleration or deceleration due to the earth’s gravitational force.

**Quantities in the Concept of Straight Motion**

**Position**

Position is the location of an object at a certain time in relation to a certain reference. To determine the position of an object, you must know what the reference is, its direction to the reference, and how far the units are.

**Example:**

Determine the positions of A and B, if the reference is point O!

We mark, the arrow to the right means positive, while the arrow to the left means negative. Remember, to determine the position of an object, we need three things, namely reference, direction, and value and units. The reference is point O. The direction if to the right of point O means positive, if to the left of point O means negative. The values and units are as follows:

XA = -4 cm

XB = 6 cm

So, we can get:

The position of point A is 4 cm to the left of point O.

The position of point B is 6 cm to the right of point O.

Because this position has a value and direction, its value is included in the vector quantity.

**Distance and Displacement**

Distance is the length of the path and object has a traveled. Distance is a scalar quantity because it only has a value. To find the distance of an object, you simply add up the length of the path traveled by the object.

And displacement is a change in the position of an object. If this displacement is a vector quantity because it has a value, it also has a direction. To find the displacement of an object, you must pay attention to the initial position of the object, the final position of the object, and the direction of the object.

**Distance formula:**

S = total length of path

Displacement formula:

X = final position – initial position

X = X2 – X1

**Average speed and velocity**

Average speed is the result of dividing the total distance traveled by an object by the time interval. Average speed is like a scalar quantity because it is related to distance. While average speed is the displacement of an object in the time interval. Average speed is related to displacement, so it is a vector quantity. Average velocity formula:

V = s / t

Average velocity formula:

V = x / t

V = X2 – X1 / t2 – t1

Instantaneous Speed and Velocity

The concept of instantaneous velocity and instantaneous speed is obtained from the distance traveled by the object’s displacement in a very short time interval. Instantaneous speed is the derivative of the position function with respect to time.

Instantaneous velocity formula:

V(t) = dx(t) / dt

**Acceleration**

Acceleration is the change in the speed of an object per unit of time. For example, when someone rides a bicycle, the initial speed is zero because it is still stationary. Then, start walking at a constant speed, along the way, the rider begins to increase the speed of the bicycle. This condition is called acceleration.

**Acceleration formula:**

a = v / t

A = v2 – v1 / t2 – t1

Acceleration is also included in vector quantities because it has a value and direction. Therefore, you must also pay attention to the direction of the object’s acceleration.

- If the acceleration is in the same direction as the object’s motion, then:

The motion will be accelerated (accelerated).

The acceleration is positive.

- If the acceleration is opposite to the object’s motion, then:

The motion will be slowed down (accelerated).

The acceleration is negative.