Medium MCQ +4 / -1 PYQ · JEE Mains 2025

An object with mass 500 g moves along x-axis with speed $v = 4\sqrt{x}$ m/s. The force acting on the object is :

  1. A <p>8 N</p>
  2. B <p>4 N</p> Correct answer
  3. C <p>5 N</p>
  4. D <p>6 N</p>

Solution

<p>To find the force acting on the object, we use the formula $ F = m \times a $, where $ F $ is the force, $ m $ is the mass, and $ a $ is the acceleration.</p> <p><p>The velocity $ v $ is given as $ v = 4 \sqrt{x} $.</p></p> <p><p>Squaring both sides, we have $ v^2 = 16x $.</p></p> <p><p>Differentiate $ v^2 $ with respect to $ x $: </p> <p>$ 2v \frac{dv}{dx} = 16 $</p></p> <p><p>Solving for $ \frac{dv}{dx} $, we find:</p> <p>$ \frac{v \, dv}{dx} = \frac{16}{2} = 8 $</p></p> <p><p>The force $ F $ is then calculated as:</p> <p>$ F = 0.5 \times 8 = 4 \, \text{N} $</p></p> <p>Thus, the force acting on the object is 4 N.</p>

About this question

Subject: Physics · Chapter: Laws of Motion · Topic: Newton's First Law

This question is part of PrepWiser's free JEE Main question bank. 56 more solved questions on Laws of Motion are available — start with the harder ones if your accuracy is >70%.

Drill 25 more like these. Every day. Free.

PrepWiser turns these solved questions into a daily practice loop. Chapter-wise drills, full mocks, AI doubt chat. No auto-renew.

Start free →