Concept Development Practice Page
9-1
Circular Motion
1. Most energy of train systems is used in starting and stopping. The rotating train platform design
saves energy, for people can board or leave a train while the train is still moving. Study the sketch
and convince yourself
that this is true. The small circular platform in the middle is stationary, and
is connected to a stationary stairway.
a. If there is to be no relative motion between the train and the edge of the platform, how fast
must the train move compared to the rim speed of the rotating platform?
b. Why is the stairway located at the center of the platform?
2. The design below shows a train that makes round trips from Station A to Station B in a
continuous loop.
a. How is the size of the round platform and train speed related to the amount of time that
passengers have for boarding?
b. Why would this rotating platform be impractical for high-speed trains?
Conceptual PHYSICS