Uniform Motion and Non Uniform Motion

Uniform Motion and Non Uniform Motion - Definition and examples

In our day to day life, we see several motions of living and non-living objects, whether birds, animals, fishes, cars, trains, etc. Masses of objects are surrounding us, some stay at rest while some are in motion. A body is said to be in motion when its point changes continuously with respect to a still object taken as a reference point. We all know that the mutual characteristic of the entire moving object is that they change their position with respect to time. For example, when the position of the car changes constantly with respect to some stationary objects like houses or schools etc. we say that a car is moving, or the car is in motion. Motion can be of two kinds.

  • 1. Uniform motion

  • 2. Non-uniform motion.

  • Uniform Motion


    In Physics, uniform motion is defined as the motion, wherein the velocity of the body travelling in a straight line remains the same. When the distance travelled by a moving thing, is same at several time intervals, regardless of the time length, the motion is said to be uniform motion.

    The graph given above, it is indicated that there is a shift of 10 meters in every minute, as there is a constant velocity with respect to time.
    \[{\text{Slope}} = \frac{{dY}}{{dX}} = \frac{{{\text{Displacement}}}}{{{\text{time}}}}\]
      > Slope=\frac{\text{d}x}{\text{d}y}=\frac{\text{Displacement}}{\text{Time}}

    Velocity (V) = \[ = \frac{d}{t}\], is constant 

    > Velocity(v)=\frac{\text{d}}{\text{t'}}is constant
    What is Uniform Motion?
    The basic form of mechanical motion is the uniform linear movement. The name itself says that it is a uniform movement of a physical point in a straight line, i.e. with the same speed. The speed of linear straight-line motion is a change in the position of the object within a given time interval. The basic distinguishing of a uniform linear movement is that the displacement is equal to the passed distance. When a body passes equal distances at equal time intervals, we say that it moves at the same speed. The relation of the distance and time to a linear uniform movement is always the same. Constant speed means that the object passes equal movements for equal time intervals, always in the same direction in a straight line. In other words, the speed is equal to zero. In the case of circular movement, all parts of the object move around the circles lying in similar planes, whose centers are on the axis of rotation. The Equations describing the rotational motion of the object can be derived from the equation of translational motion by putting in its place of the path 
    s = angle of rotation
    φ= (rad), velocity
    c = angular velocity
    ω (rad/s) acceleration a = angular acceleration α (rad/s2)
    uniform rotation (ω - const):

    Examples of uniform motions.

    1. The hr. hand of clock - It moves with uniform speed, completing movement of a specific distance in an hour.
    2. An airplane cruising at a level height and a steady speed. 
    3. A car going along a straight level road at steady speed.
     4. A vibrating spring in a sewing machine.
    5. A ship steaming on a straight course at steady speed. 
    6. A train going along the tracks at steady speed.
    7. Earth moving round the sun is a uniform motion.
    8. A cooling fan running at a constant speed. 
    9. Movement of fan.
    10. A pendulum having equal amplitudes on both sides.

    Non-uniform Motion

    Definition: Non-uniform motion is used to mean the movement in which the object does not cover the same distances in same time intervals, regardless of the length of the time intervals. Every time when the speed of the moving object changes by a different proportion at the same time interval, the motion of the body is observed as non-uniform motion.

    Above graph explains that the rate of displacement of the object varies in every minute, as the velocity increases or decreases with respect to time.

    What is Non-uniform Motion?

    Accelerated motion is part of kinematics in which changes in speed take place during motion. The momentary velocity is the velocity of the particle at a given moment of time or at a given point of the path. It is similar to the mean speed for a very short time interval. Acceleration can be defined as the ratio of the change in velocity to time taken for that change. If the body stays at a point or moves at a constant velocity, it has no acceleration.

    On the acceleration sign, a uniformly variable motion can also be a positively accelerated (a> 0) and negatively accelerated (a <0), and in relation to the initial conditions, it can be: motion without initial speed (v0 = 0) and that with an initial speed (v0 > 0).
    Uniformly variable movement is a constant acceleration movement. This means that any change in the velocity is divided by the time interval which will give the same acceleration value. 

    Examples on non-uniform motions

    Most of the motions around us are non-uniform in nature. Some of them are:

    1. A horse running
    2. A man running in a 100m race
    3. A bouncy ball
    4. A car colliding with another car
    5. Plane moving through the clouds and then landing
    6. Dragging a box from a path
    7. A bus on its way through the market
    8. A car coming to a halt
    9. A train coming to its terminating spot
    10. Movement of an asteroid

    Difference between Uniform and Non-Uniform Motion
    Basis of differenceUniform MotionNon-Uniform Motion
    Definition / meaningWhen an object moves along a straight line with a constant speed or steady speedWhen a body moves with a change in speed or direction or both.
    How much displacement is made?Makes the same displacement in equal intervals of time, however small the intervals be.Covers uneven distances in equal intervals of time
    Nature of average speedSame as the actual speed of the bodyDifferent from actual speed of the body
    Rectilinear motionAcceleration is zero (0)Acceleration is non-zero
    Distance-time graphA straight lineA curve

    Quiz on non-uniform motion

    How can you tell that an object exhibits non-uniform motion from a position-time graph?

  • A. Non-uniform motion will generate a position-time graph that is a straight line with a slope greater than 10

  • B. Non-uniform motion will generate a position-time graph that is not straight, but is curved instead

  • a. Non-uniform motion will generate a position-time graph that is a straight line with a slope less than 1

  • b. Non-uniform motion will generate a position-time graph that is a vertical line

  • What is the speeding up of the object whose motion is shown in the velocity(speed)-time graph below?

  • • 7.0 m/s2

  • • 1.5 m/s2

  • • 0.5 m/s2

  • • 12 m/s2