Question

The potential energy of $4$ -particles each of mass $1\,kg$ placed at the four vertices of a square of side length $1\,m$ is

• A. $+ 4.0\, G$
• B. $-7.5\,G$
• C. $-5.4\,G$
• D. $+ 6.3 \,G$

Answer 1

Answer: (C)

$-5.4\,G$

Answer 2

Here, $AB=BC=CD=DA=1\,m$

$BD=AC$
$=\sqrt{1^{2}+1^{2}}$
$=\sqrt{2}m$
Total potential energy
$+\left[\frac{-G\times1\times1}{DA}\right]+\left[\frac{-G\times1\times1}{BD}\right]+\left[\frac{-G\times1\times1}{AC}\right]$
$=4\times\left[\frac{-G\times1\times1}{1}\right]+2\left[\frac{-G\times1\times1}{\sqrt{2}}\right]$
$=-5.4\,G$