Question

A block of mass $10\text{kg}$ is moving in x-direction with a constant speed of $10\text{m/s}$. It is subjected to a retarding force $F=(-0.1x)\text{N}$ during its travel from $x=20\text{m}$ to $x=30\text{m}$. Its final kinetic energy will be

• A. $475\text{J}$
• B. $450\text{J}$
• C. $275\text{J}$
• D. $250\text{J}$

Answer 1

The correct option is A $475\text{J}$

Using work energy theorem,
$K_f-K_i=W$
$K_f=K_i+W=\frac{1}{2}\times 10\times {\left(10\right)}^2+{\int }_{20}^{30}(-0.1x)dx$
$K_f=475\text{J}$