The car has an initial velocity of 23 m/s and a final velocity of 0 m/s. Recall that for constant acceleration,
The car stops in 7 s, so the acceleration is
Collaboration in science is important because if only one scientist does an experiment, and gets a result, he/she could have messed. So this is where collaboration comes in. A few other scientists could try the experiment, and if they get the same answers, the result may be proven correct.
Hope this helped!
See the attached picture: