Which type of mirror has a flat surface?

Atrain departs from its station at a constant acceleration of 5 m/s. what is the speed of the train at the end of 20s?

This is the substance(s) formed in a chemical reaction.

If two students are running down the hall toward each other, trying to get to class, and they have the same mass and acceleration, what will happen when they collide? will their forces cancel out or will each one experience a reaction?