Question

Um corpo de massa 20 kg , apresenta uma energia cinética igual a 9 kj, calcule a sua velocidade . *


a) 45 m/s

b) 90 m/s

c) 36 m/s

d) 30 m/s

​

Answer 1

Resposta:

d

Explicação:

Ec=mv²/2

9000=20.v²/2

9000=10v²

v²=9000/10

v=√900

v=30m/s

Answer 2

$\Large\displaystyle\text{ \begin{gathered} \sf{ 9\,kj\xrightarrow{\times1000}\,=9000\,J} \end{gathered} }$

$\Large\displaystyle\text{ \begin{gathered} \sf{E_c=\frac{1}{2}\cdot m\cdot v^2\Leftrightarrow v=\sqrt{\frac{2\cdot E_c}{m}} } \end{gathered} }$

$\Large\displaystyle\text{ \begin{gathered} \sf{ v=\sqrt{\frac{2\cdot9000}{20}}=\sqrt{\frac{18000}{20}}}\end{gathered} }$

$\Large\displaystyle\text{ \begin{gathered} \sf{ v=\sqrt{900}=30\,m/s} \end{gathered} }$

$\huge\boxed{\boxed{\boxed{\boxed{\sf\maltese~\red{alternativa ~d}}}}}$