Motion

What is Motion?

Motion refers to the change in position of an object with respect to time and a reference point. It is described in terms of displacement, distance, speed, velocity, and acceleration. Understanding motion is essential to analyze the physical behavior of bodies.

Types of Motion

• Translatory Motion: Movement in a straight or curved line (e.g., a car on a road).
• Rotational Motion: Movement around an axis (e.g., spinning wheel).
• Oscillatory Motion: To and fro motion (e.g., pendulum).

Key Concepts

• Distance: Total path covered (scalar).
• Displacement: Shortest distance between initial and final points (vector).
• Speed: Distance per unit time (scalar).
• Velocity: Displacement per unit time (vector).
• Acceleration: Change in velocity per unit time.

Equations of Motion

• v = u + at
• s = ut + ½at²
• v² = u² + 2as

Graphical Representation

Graphs like velocity-time and distance-time help visualize motion. The slope of distance-time graph gives speed, while area under velocity-time graph gives displacement.

Previous Year Questions

• HSSC JE 2021: If a body is moving with uniform acceleration and initial velocity is 5 m/s, acceleration is 2 m/s², what is velocity after 3 seconds?
• v = u + at = 5 + (2×3) = 11 m/s
• RRB JE 2019: A car travels 100 m in 4 seconds. What is its average speed?
• Speed = Distance / Time = 100 / 4 = 25 m/s
• SSC CGL 2020: A particle covers 10 m in first 2 seconds and 20 m in next 2 seconds. What is its acceleration?
• Using s = ut + ½at², solve using two intervals. Final answer: 2.5 m/s²

Important Points

• Displacement can be zero but distance cannot be.
• Uniform motion means constant speed in a straight line.
• Acceleration is vector and can be negative (retardation).

Conclusion

Understanding motion lays the foundation for mechanics. From simple linear motion to complex circular dynamics, mastering these concepts is key to succeeding in exams and real-world physics applications.