55. A soccer ball has a mass of 0.4 kg. Initially, it moves to the left at a speed of 20 m/s, but is then kicked with a speed of 30 m/s, upwards and to the right 45°. Assuming that the collision time △t = 0.01 s, which of the following values most closely approximates the magnitude of the average kick force (in Newtons)?
(A)5
(B)180
(D)1800
(C)500
(E)5000
答案：D
統計：A:0,B:0,C:0,D:0,E:0
難度：計算中