Aspace vehicle deploys its re-entry parachute when it's traveling at a vertical velocity of -150 meters/second (negative because the parachute is going down.) it comes to rest at 0 meters/second after 30 seconds. what's the average acceleration of the shuttle during this time span?

The initial velocity is -150m/s.
Remember that:
V(t) = Vi + at, where v(t) is velocity at time t, Vi is initial velocity, and a is acceleration.
We know that the vehicle stopped after 30 seconds, so V(30) = 0.
Let's plug the useful info into our function and solve for a:
0 = -150 + a*30     Add 150 to both sides
150 = 30a             Divide both sides by 30
a = 5 m/s²
The average acceleration is 5 meters per second squared. 

the law of definite proportions states samples of a compound will always contain the same proportion of elements by mass. in other words, a given compound will always contain the same elements in the same proportions by mass.the law of multiple proportions states when two elements combine with each other to form more than one compound, then the weights of one element that combine with a fixed weight of the other are in a ratio of small whole numbers.