Tolong di jawab pakai cara yahh!!!!

13. Ek = 1/2.m.v²
450 = 1/2.4.v²
450 = 1/1 x 2 x v²
450 / 2 = v²
225 = v²
akar dari 225 = v
15 m/s = v = kecepatan

14.
s = 40 cm = 4/10 m

W = F x s
= 20 x 4/10
= 2 x 4/1 = 8 J