A student observes a body moving with constant speed along a circular path. Which of the following best represents the graphical relationship between its speed and time for one complete revolution?

1. A

   A curved line increasing with time

2. B

   A horizontal straight line parallel to the time axis

3. C

   A line sloping upwards with time

4. D

   A sinusoidal curve above the time axis

Appeared in: RRB Nsg. Superintendent-2026 (Shift -2nd)

Explanation

• The question states the body moves at a 'constant speed', which is the key piece of information.
• A graph of speed (on the y-axis) versus time (on the x-axis) for a constant value will always be a horizontal line.
• The horizontal line indicates that the speed value does not change as time progresses.
• This type of motion is known as uniform circular motion, where the magnitude of the velocity (speed) is constant, but the direction is always changing.

Why Other Options Were Wrong

• Option A: A curved line that increases with time represents non-uniform acceleration, meaning the speed is increasing at an ever-changing rate, which contradicts the 'constant speed' condition.
• Option C: A line sloping upwards represents a constant positive acceleration, meaning the speed is increasing at a steady rate. This contradicts the 'constant speed' given in the problem.
• Option D: A sinusoidal curve represents an oscillating quantity. While the components of the velocity vector (e.g., vₓ and vᵧ) in circular motion are sinusoidal, the overall speed (the magnitude of the velocity vector) is constant.

Related Visual

• Visual 1: Diagram - A graph with 'Time' on the x-axis and 'Speed' on the y-axis, showing a horizontal line to represent constant speed.
• Visual 2: Animation - An object moving in a circle at a constant speed. A velocity vector is shown, constant in length but continuously changing direction, tangent to the circle.

Clinical Relevance

• Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Graphical representation of uniform circular motion as background academic context rather than a clinical decision trigger.
• While this is a physics concept, the underlying skill of graph interpretation is critical in nursing.
• Nurses constantly interpret graphical data, such as vital sign trends on a monitor, fetal heart rate patterns, blood glucose logs, and ventilator waveforms. A flat line on a heart rate monitor (asystole) is a critical, albeit grim, example of interpreting a graph.
• Understanding that a horizontal line means 'no change' is a fundamental data literacy skill applicable across many clinical charts and monitors.

How to Approach the Question

• First, identify the key phrases in the question: 'constant speed' and 'graphical relationship between its speed and time'.
• Recognize that 'constant speed' means the value for speed does not change over the time interval.
• Understand that a 'speed vs. time' graph plots speed on the vertical (y) axis and time on the horizontal (x) axis.
• Ask yourself: If the y-value is constant while the x-value increases, what does the line look like? It must be a horizontal line.
• Evaluate the given options. 'A horizontal straight line parallel to the time axis' perfectly describes this situation.
• Eliminate other options by recalling what they represent: an upward slope means increasing speed (acceleration), a curve means non-uniform change, and a sine wave means oscillation.

Concept Tested & Keywords

• Concept Tested: Graphical representation of uniform circular motion
• Stem keywords: constant speed, circular path, graphical relationship, speed and time
• Lead-in keywords: best represents

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