College physics If a car moving at 120 ft/s takes 500.0 ft to stop after its breaks are applied, what is the magnitude of the car's acceleration?

the answer is 14.4ft/s^2 can you please explain and give more details

Aboxcar traveling at 12 m/s approaches a string of 5 identical boxcars sitting stationary on the track. the moving boxcar collides and links with the stationary cars and they all move off together along the track. what is the final speed of the cars immediately after the collision? (you may take the mass of each boxcar to be 18,537 kg.)

What are two different ways you could find the value of a? explain these methods.

What is the single most important equation in all of physics?