Answer:
6.7 /s.
Explanation:
Initial velocity = u m/s
From the question, final velocity, v = - 2u m/s
Note - (the minus sign indicates that the direction was reversed and doubled)
t = 0.45
From equation of motion,
v = u + at
Acceleration, a = (v - u)/t
= (-2u - u)/0.45
= - 3u/0.45
Acceleration, a/Original speed, u = 3/0.45
= 6.7 /s