How do you calculate speed from constant acceleration over time?

[NickPerry]

This should be a painfully simple question, and yet, I can't find the answer.

once you have calculated the net acceleration force of an object, how do you figure out how fast it will be going over X seconds?

example (taken from here: http://sciencelearn.org.nz/Contexts/Rockets/Looking-Closer/Calculating-rocket-acceleration)

the shuttle rocket has a NET thrust of 5.25 m/s and that thrust is constant for 124 seconds. how do you calculate the speed? (they get 1380 m/s)

I thought it was 5.25 x (124 ^ 2) = m / s ^ 2 but that answer is way off.
then i thought, maybe it's linear? 5.25 x 124 ? but that answer wasn't correct either..

I looked at other pages giving examples, but they all seem to skip the part where they convert the m/s to the final time frame.

help?

 

[jbriggs444]

the shuttle rocket has a NET thrust of 5.25 m/s and that thrust is constant for 124 seconds

The article says 5.25 m/s² That's not thrust. That's acceleration.

The article also says: "As the shuttle uses its propellant, it also becomes much lighter, which increases acceleration"

So the article is clear that the 5.25 is NOT constant for 124 seconds.

 

[NickPerry]

Whoops. I must have glanced over that. how about this (where I originally got stuck on)

the acceleration of a flashlight in space:

https://www.reddit.com/r/askscience/comments/dofov/does_a_flashlight_produce_thrust/

1Kg
3watt
=
10 ^ -8 Newton's of force. for 20 hours (27000 seconds)

how did he get 2.5 meters every hour after 20 hours of acceleration?

EDIT:

of course, now I figure it out:

( 3 x 10^ (-8) ) x 27000 = 0.00081 m/s x 60 = 0.0486 m/M x 60 = 2.916 meters per hour. doh >.<

(I originally forgot that they had their final answer as m/hr not m/sec)

Thank you for putting up with me!