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Motion in a straight line
The natural motion of an object travelling in a straight line is called linear motion. Newton’s First Law of Motion states that an item will continue in a straight line unless acted upon by an external force.
Linear motion can also be defined as a body travelling in a straight line with no deviations, such as an athlete running on a park’s straight track or a bullet fired from a gun moving away in a straight line.
Motion in a Straight Line
Definition
A change in the location of an object over time is referred to as motion. Rectilinear motion is the movement of an object in a straight line. The Rectilinear Motion is another name for linear motion. It is recommended to not mistake linear motion with generic motion. Linear motion, as previously stated, is a one-dimensional motion. Still, in general, a motion has both magnitude and direction, i.e. the position and velocity of an item are given as vector values.
Based on the nature of displacement, linear motion is classified into:
- Uniform motion
- Non-uniform motion
Uniform Motion | Non-uniform Motion |
A distance of the same length is covered in the same time intervals. | Unequal distances are covered in unequal time intervals. |
Zero acceleration. | Non-zero acceleration. |
Identical to the actual speed. | Different from the actual speed. |
Distance-time graph is a straight line. | Distance-time graph is a curve. |
The direction of motion remains the same. | The direction of motion changes. |
Speed of the body is constant. | Speed of the body is not constant. |
No change in velocity. | Velocity changes. |
Formulae of motion in a straight line
- v=u+at
- s=ut+½ at2
- v2=u2+2as
v= final velocity
u=initial velocity
s= displacement
a=acceleration
t=time
These could also be referred to as the kinematic equations for uniformly accelerated motion.
Kinematics graph
Position-time graph | Velocity-time graph | Acceleration-time graph | |
X-axis Y-axis | Time Position | Time Velocity | Time Acceleration |
Slope | The velocity of an object | Acceleration of an object | Jerk |
Straight slope | Uniform velocity | Uniform acceleration | Uniform jerk |
Curved slope | Velocity changes | Acceleration changes | Amount of jerk changes |
Reference point
A reference point is necessary to determine the change in the location of an object. The reference point is known as the Origin, and the system with the three reference points on a graph is known as the coordinate system since it has three axes. A frame of reference is a coordinate system with a time frame.
Position, Distance, Displacement of an object
The distance between an object and a reference point determines its exact position.
When an object moves, the amount it moves is commonly referred to as the distance. There is no need for a reference point or a direction for measuring distance.
The displacement of an object refers to the change in its position. Because the final position can be in either a positive or negative direction along the number line from the initial position, the displacement must contain a direction.
Conclusion
- Linear motion, also known as rectilinear motion, is defined as motion in a straight line.
- Distance is the length traversed by an object travelling in any direction or even changing direction.
- Position refers to an object’s location in a frame of reference.
- A number line can be used to illustrate positions in straight-line motion.
- Displacement is the shortest distance between the initial and final positions.
