# 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.

Can also be done as a SGA.

## 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.

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