Question

A particle of mass $2 \,mg$ moves with constant speed and is found to pass two points $5.0 \,m$ apart in a time interval of $5\, ms$ . Find the kinetic energy of the particle

• A. 1.0 J
• B. 2.0 J
• C. $3.0 \, J$
• D. $4.0 \, J$

Answer 1

Answer: (A)

Given, mass $=2mg=2\times 10^{-6}\,kg$
Distance $= 5.0\, m$
Time $t=5\,ms=5\times10^{-3}\,s$
To find $KE$ = ?
Now, velocity $\frac{\text{Distance}}{\text{Time}}=\frac{5}{5\times10^{-3}} m/ s$
$=1000\, m/ s$
and $KE =\frac{1}{2} mv^{2}=\frac{1}{2}\times2\times10^{-6}\left(10^{3}\right)^{2}$
$=1 J$