Rocket-powered sleds are been used to test the responses of humans to acceleration. starting from rest, one sled can reach a speed of 651 m / s in 2 . 53 s and can be brought to a stop again in 3 . 37 s. find the acceleration of the sled while accelerating.
find the acceleration of the sled when braking.
answer in units of m/s^2.

Hi, I crunched some numbers for you and got the following results:

Starting from initial velocity of zero (rest) the sled reached a top speed of 257.3 m/s^2.
Upon slowing down or braking, the sled slowed down very hard to about 76.35 m/s^2.
Acceleration and Gravitational Acceleration were the main interpretations obviously in this problem. 
Also, if my math was correct, the speed of the sled slowing down was around 7.7 G's (acceleration due to gravity)! That is about on par with the acceleration of a F-16 Fighter Jet pulling out of a dive!--> (79 m/s^2) The human test subject probably came close to blacking out I would guess as well or very close to!