A certain type of rocket sled is used to measure the effects of extreme deceleration. The sled reaches a velocity of +320 km/h, then comes to a complete stop in 0.18 s. What is the average acceleration that takes place in this time interval?

2 answers

320 km/hr * 1000m/km * 1hr/3600s = 88.889 m/s
so a = -88.889/0.18 = -493.83 m/s^2
Why put a negative sign