Velocity-Time Graph

Introduction

A velocity-time graph shows how the velocity of an object changes with time. In this graph, time is taken on the X-axis and velocity is taken on the Y-axis. It helps us understand whether the object is moving with constant velocity, accelerating, slowing down, or at rest.

What Does a Velocity-Time Graph Show?

A velocity-time graph gives information about the change in velocity with time. If the graph is a horizontal straight line, the object has constant velocity. If the graph slopes upward, the velocity is increasing. If the graph slopes downward, the velocity is decreasing. If the graph lies on the time axis, the object is at rest.

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Uniform Velocity

When an object moves with constant velocity, its velocity does not change with time. Therefore, the velocity-time graph is a horizontal straight line parallel to the time axis.

Example: A bus moves with a constant velocity of 10 m/s for 5 s.

Illustration of Uniform Velocity:

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Uniform Acceleration

When the velocity of an object increases by equal amounts in equal intervals of time, the object is said to have uniform acceleration. The velocity-time graph is a straight line with positive slope.

Example: A car accelerates uniformly from rest to 20 m/s in 5 s.

Illustration of Uniform Acceleration:

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Uniform Retardation

When the velocity of an object decreases by equal amounts in equal intervals of time, the object is said to have uniform retardation. The velocity-time graph is a straight line with negative slope.

Example: A bike slows down uniformly from 20 m/s to 0 in 5 s.

Illustration of Uniform Retardation:

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Object at Rest

When an object is at rest, its velocity is zero. Therefore, the velocity-time graph lies along the time axis.

Example: A parked car remains at rest for 10 s.

Illustration of Object at Rest:

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Important Points

• A horizontal line above the time axis shows constant velocity.
• An upward sloping straight line shows uniform acceleration.
• A downward sloping straight line shows uniform retardation.
• A line along the time axis shows that the object is at rest.
• The slope of a velocity-time graph represents acceleration.

Conclusion

A velocity-time graph is very useful in understanding how the velocity of an object changes with time. By looking at the graph, we can easily know whether the object is moving with constant velocity, accelerating, slowing down, or not moving at all.