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NDA 2018 GAT · General Knowledge · Motion, Forces and Gravitation · medium

A constant force of 20 N acts on a body of mass 5 kg initially at rest. Its speed after 3 s is

Single correct option

A constant force of 20 N acts on a body of mass 5 kg initially at rest. Its speed after 3 s is
  1. A. 4 m/s
  2. B. 12 m/s
  3. C. 60 m/s
  4. D. 15 m/s
Show answer and solution

Answer: (B) 12 m/s

Acceleration is a = F/m = 20/5 = 4 m/s², and from rest v = at = 4 × 3 = 12 m/s. The value 4 m/s is just the acceleration, 60 m/s multiplies force by time without dividing by mass, and 15 m/s comes from inverting the mass-force ratio. Newton's second law links the force, mass and acceleration.
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Original question written in the NDA 2018 GAT pattern and checked twice for the correct answer. Not an official question paper. How we write and check questions · Corrections policy · Report a mistake