# Uniform linear motion

### Definition of the uniform linear motion

An object experiences uniform linear motion if the velocity of the object is constant. Velocity includes the magnitude and direction of velocity. Direction of velocity = direction of displacement = direction of movement. The direction of the velocity of a constant object = the direction of motion of a constant object or the direction of motion of a fixed object = the object is moving straight. The magnitude of velocity or speed is constant = the speed is always the same all the time.

If the speed of the object is 10 m/s, as long as the object moves, the speed of the object is still 10 m/s. If an object moves at a constant speed of 10 m/s, for example, the object moves 10 meters per second. One second later, the object moves 10 meters from its original position when the object starts moving at a constant speed of 10 m/s. Two seconds later, the object moves 20 meters from its original position. Three seconds later, the object moves as far as 30 meters from its original position. Etc. If an object moves at a constant speed of 20 m/s, for example, the object moves 20 meters per second. One second later, the object moves 20 meters from its original position when the object starts moving at a constant speed of 20 m/s. Two seconds later, the object moves 40 meters from its original position. Three seconds later, the object moves as far as 60 meters from its original position. Etc.

Uniform linear motion is motion with a constant velocity (magnitude and direction of velocity are constant) therefore there is no acceleration. It should be noted that uniform linear motion that occurs on the surface of the earth only occurs in the horizontal direction.

### The equation of the uniform linear motion

Equations or formulas in uniform linear motion explain the relationship between physical quantities in uniform linear motion. There are several physical quantities in uniform linear motion, include time interval (t), distance (d), and speed (v). The relationship between these three physical quantities expressed through the equation:

v = d / t

v = speed (SI unit of speed in meters per second, abbreviated m/s)

d = distance (SI unit of distance is meter, abbreviated m)

t = time (SI unit of time is second, abbreviated s)

Sample problem 1 (without formula):

A particle moves straight at a constant speed of 10 m/s.

a) What is the particle’s speed after moving for 2 seconds?

b) What is the distance after moving for 5 seconds?

Solution:

a) Constant speed = 10 m/s.

b) 10 m/s means 10 meters each 1 second. 50 meters after 5 seconds.

Sample problem 2 (without formula):

A car moves with a constant speed of 60 km/h. What is the distance after a move for 10 minutes?

Solution:

60 km / h = 60 km / 60 minutes = 1 km / minute = 10 km / 10 minutes.