If a train going 60 m/s hits the breaks, and it takes the train 85 seconds to stop, what is the train´s acceleration

Acceleration is change in velocity over time -->

Δv or change in velocity equals the Final velocity minus the initial velocity

Our initial velocity here is 60m/s while our final velocity is 0 m/s

The time interval is 85 seconds so...

The negative is there to indicate that the train in slowing down or decelerating

the first american roller coaster was the mauch chunk switchback railway, built in the mountains of pennsylvania in the mid-1800s. the track, originally built to send coal to a railway, was reconfigured as a "scenic tour."

less than one you can't create energy