# 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.

1. What is uniform linear motion?

Uniform linear motion is a motion in a straight line at a constant speed or velocity.

2. What is the formula for uniform linear motion?

The formula is s = vt, where s is the displacement or distance, v is the velocity, and t is the time taken.

3. Can a body at rest be said to be in uniform linear motion?

Yes, a body at rest can be considered to be in uniform linear motion with a velocity of zero.

4. What does the slope of a distance-time graph in uniform linear motion represent?

The slope of a distance-time graph in uniform linear motion represents the speed or velocity of the object.

5. Can an object in uniform linear motion have acceleration?

No, an object in uniform linear motion cannot have acceleration as its velocity is constant.

6. What is the unit of velocity in the International System of Units (SI)?

The unit of velocity in SI is meter per second (m/s).

7. What is the relationship between speed and velocity in uniform linear motion?

In uniform linear motion, speed is the magnitude of velocity. If the motion is in a fixed direction, speed and velocity are numerically equal.

8. What is the significance of the ‘t’ in the uniform linear motion formula s = vt?

‘t’ represents the time interval during which the motion occurred.

9. What happens to the displacement ‘s’ in uniform linear motion when the time ‘t’ doubles?

In uniform linear motion, if the time ‘t’ doubles, the displacement ‘s’ will also double, as displacement is directly proportional to time.

10. What happens to the displacement ‘s’ in uniform linear motion when the velocity ‘v’ becomes zero?

When the velocity ‘v’ becomes zero, the displacement ‘s’ also becomes zero. This corresponds to an object at rest.

1. How is uniform linear motion different from uniformly accelerated motion?

In uniform linear motion, velocity is constant, whereas in uniformly accelerated motion, velocity changes at a constant rate.

1. How does changing the velocity affect the uniform linear motion of an object?

Since uniform linear motion is characterized by constant velocity, any change in velocity would mean the motion is no longer uniform and linear.

1. Can the displacement ‘s’ be negative in uniform linear motion?

Yes, displacement ‘s’ can be negative in uniform linear motion. This would indicate motion in the opposite direction to the chosen positive direction.

1. How can one identify uniform linear motion in a velocity-time graph?

Uniform linear motion is represented by a horizontal line in a velocity-time graph, indicating that the velocity is constant over time.

1. What is the role of forces in uniform linear motion?

If no net forces act on an object (or if all forces balance out), the object can continue moving with constant velocity, that is, in uniform linear motion. This is in line with Newton’s first law of motion.

1. How is time ‘t’ measured in uniform linear motion?

Time ‘t’ is typically measured from the start of the observed motion until the end of the observed motion.

1. Is it possible for an object in uniform linear motion to come to a stop?

An object in uniform linear motion will not come to a stop unless acted upon by an external force. This is based on Newton’s first law of motion.

1. What does it mean for an object to be in uniform linear motion in space?

An object in uniform linear motion in space moves at a constant velocity along a straight line, and it will continue to do so unless acted upon by an external force.

1. Can two objects be in uniform linear motion relative to each other?

Yes, if two objects are moving in the same direction at the same constant velocity, they are in uniform linear motion relative to each other.

1. Can we apply the formula for uniform linear motion (s = vt) to an object moving in a circular path at a constant speed?

No, we cannot. Although the speed might be constant for an object moving in a circular path, the velocity is not constant because its direction is constantly changing. The formula s = vt applies strictly to uniform linear motion.