# Linear Acceleration

## Prompts

** “What is the trajectory of a ball thrown straight up on the station
platform,
as seen by a train going through the station?” **

** “What if the train is accelerating?” **

## Context

*Estimated Time: 15 minutes, including wrap-up*

This SWBQ requires basic familiarity with Newtonian mechanics for constant acceleration. Students are asked to draw the trajectory of a ball thrown straight up on the station platform as seen from a train accelerating through the station, for several values of the (constant) acceleration.

- The accelerating case is (at first) counterintuitive.
- This activity sets the stage for rotational acceleration.

## Wrap Up

- First discuss the case of zero acceleration, but nonzero velocity.
- Then slowly increase the acceleration (opposite to the velocity).
- Is a boomerang trajectory possible?
- Which way does gravity (appear to) point on the train?
- Show prepared pictures if appropriate.

See this page for further discussion.