If the speed of an object moving along a straight line keeps changing with time, what is the nature of its motion called?

Introduction / Context:

This question is about basic classification of motion in kinematics. When describing how an object moves along a path, we often distinguish between uniform and non uniform motion. Recognising these types helps in selecting the correct equations and graphs, such as distance time and velocity time relations.

Given Data / Assumptions:

• An object moves along a straight line path.
• The speed of the object is not constant; it keeps changing with time.
• We are asked to name the type of motion based on this behaviour of speed.
• We assume one dimensional motion with no complications like oscillations.

Concept / Approach:

Uniform motion in a straight line means that the object covers equal distances in equal intervals of time and has constant speed. Non uniform motion means that the speed changes from one moment to another, so distances covered in equal time intervals are not the same. Periodic motion refers to motion that repeats after a fixed time, and circular motion refers to motion along a circular path. Since the object in this question is in a straight line and its speed keeps changing, the correct description is non uniform motion.

Step-by-Step Solution:

Verification / Alternative check:

Consider a car driving in city traffic along a straight road. The driver speeds up, slows down, and sometimes stops, so the speed is not constant. Distances covered in each minute vary. This is a real life example of non uniform motion. By contrast, a vehicle on a cruise control system on a straight highway at steady speed is in uniform motion. Drawing distance time graphs also shows that uniform motion has a straight line graph, whereas non uniform motion produces a curve, further emphasising the difference.

Why Other Options Are Wrong:

• Uniform motion: Requires constant speed, which contradicts the information that speed keeps changing.
• Periodic motion: Describes motion that repeats at regular time intervals, such as pendulum oscillation, not stated here.
• Circular motion: Involves a curved circular path, but the question specifies a straight line path.

Common Pitfalls:

Students sometimes confuse non uniform motion with random motion, but non uniform simply means speed or direction changes. Others might mistake periodic motion for any motion that changes, but periodic is more specific and requires regular repetition. Keeping the definitions precise helps classify motions correctly: constant speed means uniform, changing speed or direction means non uniform, repeated cycles mean periodic, and curved closed path suggests circular motion.

Final Answer:

If the speed along a straight line keeps changing, the motion is called non uniform motion.