Question

Ec=3000j V=60km/h m=? ​

Answer 1

$v=60 km/h=16,66 m/s\\Ec=\frac{mv^2}{2}=>m=\frac{2Ec}{v^2}=\frac{2*3000}{16,66^2}=\frac{6000}{277,77}=21,6 kg$