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 $KE =\frac{1}{2} mv^{2}=\frac{1}{2}\times2\times10^{-6}\left(10^{3}\right)^{2}$
$=1 J$