Question

A block of mass 10 kg, moving in x direction with a constant speed of 10 $m{s}^{-1}$, is subjected to a retarding force $F=0.1\times J/m$ during its travel from x = 20 m to 30 m. Its final KE will be:

Answer 1

Given mass $m=10kg$ ,Force$=0.1\times j/m$,Initial velocity=$10m/se{c}^2$

$F=ma$

$0.1x=10a$

a=$\frac{\left(0.1x\right)}{10}$

$v^2=u^2-2as$

$100-2\times \frac{0.1}{10}\times 10$

$S=(30-20=10=10m=x)$

$=100-2=98$

Now kinetic energy$KE=\frac{1}{2}m{v}^2$

$=\frac{1}{2}\times 10\times 98$

$=490j$