Răspuns :
[tex]v=72 \frac{km}{h} =\frac{72*1000}{3600} =20\frac{m}{s} \\E_{c} =\frac{mv^{2} }{2}\\E_{c}=\frac{800*20^{2} }{2} \\E_{c} =160000J[/tex]
Răspuns:
160000 J = 160 kJ
Explicație:
Ec = mv²/2
v = 72km/h = 72000m/3600s = 20 m/s
Ec = 800kg×(400m²/s²)/2 = 160000 J = 160 kJ
Obs.
1 J = kg×m²/s²