Resposta:
Energia cinética:
[tex]\sf E_c=\dfrac{m\cdot v^2}{2}[/tex]
de um caminhão (dados no enunciado):
[tex]\sf {E_c}_{\,caminhao}=\dfrac{(20~t)\cdot (72~km/h)^2}{2}[/tex]
[tex]\sf {E_c}_{\,caminhao}=\dfrac{(20000~kg)\cdot (20~m/s)^2}{2}[/tex]
[tex]\sf {E_c}_{\,caminhao}=\dfrac{20000\cdot400}{2}[/tex]
[tex]\sf {E_c}_{\,caminhao}=10000\cdot400[/tex]
[tex]\red{\sf {E_c}_{\,caminhao}=4000000~J}[/tex]
de um astronauta (dados no enunciado):
[tex]\sf {E_c}_{\,astronauta}=\dfrac{(60~kg)\cdot (28800~km/h)^2}{2}[/tex]
[tex]\sf {E_c}_{\,astronauta}=\dfrac{60\cdot (8000~m/s)^2}{2}[/tex]
[tex]\sf {E_c}_{\,astronauta}=\dfrac{60\cdot64000000}{2}[/tex]
[tex]\sf {E_c}_{\,astronauta}=30\cdot64000000[/tex]
[tex]\red{\sf {E_c}_{\,astronauta}=1920000000~J}[/tex]
Razão entre as energias:
[tex]\sf \dfrac{{E_c}_{\,caminhao}}{{E_c}_{\,astronauta}}=\dfrac{4000000}{1920000000}=\dfrac{4}{1920}=\red{\dfrac{1}{480}}[/tex]
