Question

qual a energia cinética de uma particula de massa 5000g cuja velocidade vale 72 km/h ? ,

Answer 1

Epc= m.v^2/2            m = 5000/1000 = 5kg e  72 ÷ 3,6 = 20 m/s
Epc = (5 . 20^2)/2
Epc= 2000 / 2
Epc= 1000J

Answer 2

$\sf m=5000\,g$

$\sf m=5\,kg$

$\sf v=72\,km/h$

$\sf v=20\,m/s$

$\sf E_c=\dfrac{1}{2}\cdot m\cdot v^2$

$\sf E_c=\dfrac{1}{2}\cdot5\cdot20^2$

$\sf E_c=2{,}5\cdot400$

$\boxed{\boxed{\sf E_c=1000\,J}}$