A stone is thrown vertically downwards with a speed of 5 m/s from the top of a tower. What will be its velocity after 2 seconds? (Take g = 10 m/s²)

Appeared in: RRB Nsg. Superintendent-2026 (Shift -1st)

Explanation

The problem involves an object moving with constant acceleration (gravity), so the kinematic equations of motion apply.
The first equation of motion, v = u + at, relates final velocity (v), initial velocity (u), acceleration (a), and time (t).
The given values are: initial velocity (u) = 5 m/s, acceleration (a) = g = 10 m/s², and time (t) = 2 s.
Since the motion is downwards, both initial velocity and acceleration due to gravity are in the same direction and can be treated as positive values.
Substituting the values into the formula gives: v = 5 + (10 × 2) = 5 + 20 = 25 m/s.

Option A: This result is calculated by assuming the initial velocity (u) is 0 m/s (v = 0 + 10 × 2). However, the problem states the stone was thrown with an initial speed of 5 m/s.
Option C: This result is obtained by using a time (t) of 1 second instead of 2 seconds (v = 5 + 10 × 1).
Option D: This result does not follow from the given values. It could arise from a calculation error or assuming an incorrect initial velocity, such as 10 m/s (v = 10 + 10 × 2).

Visual 1: Diagram - A diagram showing a stone being thrown downwards from a tower. Vectors should illustrate the initial velocity (u), the constant downward acceleration due to gravity (g), and the final velocity (v) after time (t). This helps visualize the vector quantities.
Visual 2: Infographic - A chart summarizing the three main equations of motion for constant linear acceleration, with the equation v = u + at highlighted for this specific problem.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Equations of motion for an object under constant acceleration (gravity) as background academic context rather than a clinical decision trigger.
This question tests fundamental physics principles (kinematics), which are often included in the general science or aptitude sections of nursing entrance examinations.
While not a direct nursing skill, understanding concepts like velocity and acceleration provides a foundational knowledge for biomechanics, which is relevant to understanding trauma from falls, accidents, and other injuries.
What if? If the stone were thrown upwards with a speed of 5 m/s, the initial velocity would be in the opposite direction to gravity. Taking the downward direction as positive, the initial velocity would be u = -5 m/s. The velocity after 2 seconds would be v = -5 + (10 × 2) = 15 m/s, indicating it is moving downwards at 15 m/s.

How to Approach the Question

First, identify and list all the known quantities provided in the problem: initial velocity (u), acceleration (a), and time (t).
Note the direction of motion. The stone is thrown 'vertically downwards', so the initial velocity (u = 5 m/s) and the acceleration due to gravity (g = 10 m/s²) are in the same direction.
Select the appropriate kinematic equation that connects the unknown variable (final velocity, v) with the known variables. The correct equation here is v = u + at.
Substitute the known values into the chosen equation: v = 5 + (10 × 2).
Perform the mathematical calculation to solve for the final velocity, v.
Finally, compare your calculated result with the given options to select the correct answer.

Concept Tested & Keywords

Concept Tested: Equations of motion for an object under constant acceleration (gravity).
Stem keywords: stone, vertically downwards, speed, 5 m/s, tower, velocity, 2 seconds, g = 10 m/s²
Lead-in keywords: What will be

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Practise the full RRB Nsg. Superintendent-2026 (Shift -1st)

Attempt every question from this paper in a timed mock, then review the full solution for each one.