In a springy collision, if the fast moving trolley collides with a slow
one, then the fast one will bounce back at speed of
A. slow one
B. less than slow one
C. more than slow one
D. with the same speed as before
one, then the fast one will bounce back at speed of
A. slow one
B. less than slow one
C. more than slow one
D. with the same speed as before